diff --git a/re_test.go b/re_test.go
index ba26fe6..06189ce 100644
--- a/re_test.go
+++ b/re_test.go
@@ -322,6 +322,114 @@ var reTests = []struct {
 	{`a[b-]`, nil, `a-`, []Group{{0, 2}}},
 	{`a[b-a]`, nil, `a-`, nil},
 
+	// Case-insensitive matching tests
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, `XBC`, []Group{}},
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, `AXC`, []Group{}},
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABX`, []Group{}},
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, `XABCY`, []Group{{1, 4}}},
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABABC`, []Group{{2, 5}}},
+	{`ab*c`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`ab*bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`ab*bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBC`, []Group{{0, 4}}},
+	{`ab*bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{{0, 6}}},
+	{`ab{0,}c`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{{0, 6}}},
+	{`ab+bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBC`, []Group{{0, 4}}},
+	{`ab+bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{}},
+	{`ab+bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABQ`, []Group{}},
+	{`ab{1,}bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABQ`, []Group{}},
+	{`ab+bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{{0, 6}}},
+	{`ab{1,}bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{{0, 6}}},
+	{`ab{1,3}bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{{0, 6}}},
+	{`ab{3,4}bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{{0, 6}}},
+	{`ab{4,5}bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{}},
+	{`ab?bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBC`, []Group{{0, 4}}},
+	{`ab?bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`ab{0,1}bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`ab?bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBBC`, []Group{}},
+	{`ab?c`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`^abc$`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`^abc$`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCC`, []Group{}},
+	{`^abc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCC`, []Group{{0, 3}}},
+	{`^abc$`, []ReFlag{RE_CASE_INSENSITIVE}, `AABC`, []Group{}},
+	{`abc$`, []ReFlag{RE_CASE_INSENSITIVE}, `AABC`, []Group{{1, 4}}},
+	{`^`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 0}}},
+	{`$`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{3, 3}}},
+	{`a.c`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 3}}},
+	{`a.c`, []ReFlag{RE_CASE_INSENSITIVE}, `AXC`, []Group{{0, 3}}},
+	{`a.*c`, []ReFlag{RE_CASE_INSENSITIVE}, `AXYZC`, []Group{{0, 5}}},
+	{`a.*c`, []ReFlag{RE_CASE_INSENSITIVE}, `AXYZD`, []Group{}},
+	{`a[bc]d`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{}},
+	{`a[bc]d`, []ReFlag{RE_CASE_INSENSITIVE}, `ABD`, []Group{{0, 3}}},
+	{`a[b-d]e`, []ReFlag{RE_CASE_INSENSITIVE}, `ABD`, []Group{}},
+	{`a[b-d]e`, []ReFlag{RE_CASE_INSENSITIVE}, `ACE`, []Group{{0, 3}}},
+	{`a[b-d]`, []ReFlag{RE_CASE_INSENSITIVE}, `AAC`, []Group{{1, 3}}},
+	{`a[-b]`, []ReFlag{RE_CASE_INSENSITIVE}, `A-`, []Group{{0, 2}}}, // If a character class has a hyphen without a start or end character, it is treated as a literal hyphen
+	{`a[\-b]`, []ReFlag{RE_CASE_INSENSITIVE}, `A-`, []Group{{0, 2}}},
+	{`a[b-]`, []ReFlag{RE_CASE_INSENSITIVE}, `A-`, []Group{{0, 2}}}, // If a character class has a hyphen without a start or end character, it is treated as a literal hyphen
+
+	{`a[]b`, []ReFlag{RE_CASE_INSENSITIVE}, `-`, nil},
+	{`a[`, []ReFlag{RE_CASE_INSENSITIVE}, `-`, nil},
+	{`a\`, []ReFlag{RE_CASE_INSENSITIVE}, `-`, nil},
+	{`abc)`, []ReFlag{RE_CASE_INSENSITIVE}, `-`, nil},
+	{`(abc`, []ReFlag{RE_CASE_INSENSITIVE}, `-`, nil},
+	{`a]`, []ReFlag{RE_CASE_INSENSITIVE}, `A]`, []Group{{0, 2}}},
+	{`a[]]b`, []ReFlag{RE_CASE_INSENSITIVE}, `A]B`, []Group{{0, 3}}},
+	{`a[\]]b`, []ReFlag{RE_CASE_INSENSITIVE}, `A]B`, []Group{{0, 3}}},
+	{`a[^bc]d`, []ReFlag{RE_CASE_INSENSITIVE}, `AED`, []Group{{0, 3}}},
+	{`a[^bc]d`, []ReFlag{RE_CASE_INSENSITIVE}, `ABD`, []Group{}},
+	{`a[^-b]c`, []ReFlag{RE_CASE_INSENSITIVE}, `ADC`, []Group{{0, 3}}},
+	{`a[^-b]c`, []ReFlag{RE_CASE_INSENSITIVE}, `A-C`, []Group{}},
+	{`a[^]b]c`, []ReFlag{RE_CASE_INSENSITIVE}, `A]C`, []Group{}},
+	{`a[^]b]c`, []ReFlag{RE_CASE_INSENSITIVE}, `ADC`, []Group{{0, 3}}},
+	{`\ba\b`, []ReFlag{RE_CASE_INSENSITIVE}, `A-`, []Group{{0, 1}}},
+	{`\ba\b`, []ReFlag{RE_CASE_INSENSITIVE}, `-A`, []Group{{1, 2}}},
+	{`\ba\b`, []ReFlag{RE_CASE_INSENSITIVE}, `-A-`, []Group{{1, 2}}},
+	{`\by\b`, []ReFlag{RE_CASE_INSENSITIVE}, `XY`, []Group{}},
+	{`\by\b`, []ReFlag{RE_CASE_INSENSITIVE}, `YZ`, []Group{}},
+	{`\by\b`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{}},
+	{`x\b`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{}},
+	{`x\B`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{{0, 1}}},
+	{`\Bz`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{{2, 3}}},
+	{`z\B`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{}},
+	{`\Bx`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{}},
+	{`\Ba\B`, []ReFlag{RE_CASE_INSENSITIVE}, `A-`, []Group{}},
+	{`\Ba\B`, []ReFlag{RE_CASE_INSENSITIVE}, `-A`, []Group{}},
+	{`\Ba\B`, []ReFlag{RE_CASE_INSENSITIVE}, `-A-`, []Group{}},
+	{`\By\B`, []ReFlag{RE_CASE_INSENSITIVE}, `XY`, []Group{}},
+	{`\By\B`, []ReFlag{RE_CASE_INSENSITIVE}, `YZ`, []Group{}},
+	{`\By\b`, []ReFlag{RE_CASE_INSENSITIVE}, `XY`, []Group{{1, 2}}},
+	{`\by\B`, []ReFlag{RE_CASE_INSENSITIVE}, `YZ`, []Group{{0, 1}}},
+	{`\By\B`, []ReFlag{RE_CASE_INSENSITIVE}, `XYZ`, []Group{{1, 2}}},
+	{`ab|cd`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Group{{0, 2}}},
+	{`ab|cd`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Group{{0, 2}, {2, 4}}},
+	{`$b`, []ReFlag{RE_CASE_INSENSITIVE}, `B`, []Group{}},
+	{`a\(b`, []ReFlag{RE_CASE_INSENSITIVE}, `A(B`, []Group{{0, 3}}},
+	{`a\(*b`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Group{{0, 2}}},
+	{`a\(*b`, []ReFlag{RE_CASE_INSENSITIVE}, `A((B`, []Group{{0, 4}}},
+	{`a\\b`, []ReFlag{RE_CASE_INSENSITIVE}, `A\B`, []Group{{0, 3}}},
+	{`a+b+c`, []ReFlag{RE_CASE_INSENSITIVE}, `AABBABC`, []Group{{4, 7}}},
+	{`a{1,}b{1,}c`, []ReFlag{RE_CASE_INSENSITIVE}, `AABBABC`, []Group{{4, 7}}},
+	{`)(`, []ReFlag{RE_CASE_INSENSITIVE}, `-`, nil},
+	{`[^ab]*`, []ReFlag{RE_CASE_INSENSITIVE}, `CDE`, []Group{{0, 3}, {3, 3}}},
+	{`abc`, []ReFlag{RE_CASE_INSENSITIVE}, ``, []Group{}},
+	{`a*`, []ReFlag{RE_CASE_INSENSITIVE}, ``, []Group{{0, 0}}},
+	{`a|b|c|d|e`, []ReFlag{RE_CASE_INSENSITIVE}, `E`, []Group{{0, 1}}},
+	{`abcd*efg`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDEFG`, []Group{{0, 7}}},
+	{`ab*`, []ReFlag{RE_CASE_INSENSITIVE}, `XABYABBBZ`, []Group{{1, 3}, {4, 8}}},
+	{`ab*`, []ReFlag{RE_CASE_INSENSITIVE}, `XAYABBBZ`, []Group{{1, 2}, {3, 7}}},
+	{`[abhgefdc]ij`, []ReFlag{RE_CASE_INSENSITIVE}, `HIJ`, []Group{{0, 3}}},
+	{`a[bcd]*dcdcde`, []ReFlag{RE_CASE_INSENSITIVE}, `ADCDCDE`, []Group{{0, 7}}},
+	{`a[bcd]+dcdcde`, []ReFlag{RE_CASE_INSENSITIVE}, `ADCDCDE`, []Group{}},
+	{`[a-zA-Z_][a-zA-Z0-9_]*`, []ReFlag{RE_CASE_INSENSITIVE}, `ALPHA`, []Group{{0, 5}}},
+	{`multiple words of text`, []ReFlag{RE_CASE_INSENSITIVE}, `UH-UH`, []Group{}},
+	{`multiple words`, []ReFlag{RE_CASE_INSENSITIVE}, `MULTIPLE WORDS, YEAH`, []Group{{0, 14}}},
+	{`[k]`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Group{}},
+	{`a[-]?c`, []ReFlag{RE_CASE_INSENSITIVE}, `AC`, []Group{{0, 2}}},
+	{`^(.+)?B`, []ReFlag{RE_CASE_INSENSITIVE}, `ab`, []Group{{0, 2}}},
+	{`\0009`, []ReFlag{RE_CASE_INSENSITIVE}, "\x009", []Group{{0, 2}}},
+	{`\141`, []ReFlag{RE_CASE_INSENSITIVE}, "A", []Group{{0, 1}}},
+
 	// Todo - add numeric range tests
 }
 
@@ -405,6 +513,56 @@ var groupTests = []struct {
 	{`([abc])*d`, nil, `abbbcd`, []Match{[]Group{{0, 6}, {4, 5}}}},
 	{`([abc])*bcd`, nil, `abcd`, []Match{[]Group{{0, 4}, {0, 1}}}},
 	{`^(ab|cd)e`, nil, `abcde`, []Match{}},
+
+	// Case-insensitive tests
+	{`(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(l)\071`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDEFGHIJKL9`, []Match{[]Group{{0, 13}, {0, 1}, {1, 2}, {2, 3}, {3, 4}, {4, 5}, {5, 6}, {6, 7}, {7, 8}, {8, 9}, {9, 10}, {10, 11}, {11, 12}}}},
+	{`()ef`, []ReFlag{RE_CASE_INSENSITIVE}, `DEF`, []Match{[]Group{{1, 3}, {1, 1}}}},
+	{`(?:)ef`, []ReFlag{RE_CASE_INSENSITIVE}, `DEF`, []Match{[]Group{{1, 3}}}},
+	{`(?:)`, []ReFlag{RE_CASE_INSENSITIVE}, `DEF`, []Match{[]Group{{0, 0}}, []Group{{1, 1}}, []Group{{2, 2}}, []Group{{3, 3}}}},
+	{`((a))`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Match{[]Group{{0, 1}, {0, 1}, {0, 1}}}},
+	{`(a)b(c)`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Match{[]Group{{0, 3}, {0, 1}, {2, 3}}}},
+	{`(a+|b)*`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 2}, {1, 2}}, []Group{{2, 2}}}},
+	{`(a+|b){0,}`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 2}, {1, 2}}, []Group{{2, 2}}}},
+	{`(a+|b)+`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 2}, {1, 2}}}},
+	{`(a+|b){1,}`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 2}, {1, 2}}}},
+	{`(a+|b)?`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 1}, {0, 1}}, []Group{{1, 2}, {1, 2}}, []Group{{2, 2}}}},
+	{`(a+|b){0,1}`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 1}, {0, 1}}, []Group{{1, 2}, {1, 2}}, []Group{{2, 2}}}},
+	{`(a|b|c|d|e)f`, []ReFlag{RE_CASE_INSENSITIVE}, `EF`, []Match{[]Group{{0, 2}, {0, 1}}}},
+	{`(ab|cd)e`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDE`, []Match{[]Group{{2, 5}, {2, 4}}}},
+	{`^(ab|cd)e`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDE`, []Match{}},
+	{`(abc|)ef`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDEF`, []Match{[]Group{{4, 6}, {4, 4}}}},
+	{`(a|b)c*d`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Match{[]Group{{1, 4}, {1, 2}}}},
+	{`(ab|ab*)bc`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Match{[]Group{{0, 3}, {0, 1}}}},
+	{`a([bc]*)c*`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Match{[]Group{{0, 3}, {1, 3}}}},
+	{`a([bc]*)(c*d)`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Match{[]Group{{0, 4}, {1, 3}, {3, 4}}}},
+	{`a([bc]+)(c*d)`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Match{[]Group{{0, 4}, {1, 3}, {3, 4}}}},
+	{`a([bc]*)(c+d)`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Match{[]Group{{0, 4}, {1, 2}, {2, 4}}}},
+	{`(ab|a)b*c`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Match{[]Group{{0, 3}, {0, 2}}}},
+	{`((a)(b)c)(d)`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Match{[]Group{{0, 4}, {0, 3}, {0, 1}, {1, 2}, {3, 4}}}},
+	{`^a(bc+|b[eh])g|.h$`, []ReFlag{RE_CASE_INSENSITIVE}, `ABH`, []Match{[]Group{{1, 3}}}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, []ReFlag{RE_CASE_INSENSITIVE}, `EFFGZ`, []Match{[]Group{{0, 5}, {0, 5}}}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, []ReFlag{RE_CASE_INSENSITIVE}, `IJ`, []Match{[]Group{{0, 2}, {0, 2}, {1, 2}}}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, []ReFlag{RE_CASE_INSENSITIVE}, `EFFG`, []Match{}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, []ReFlag{RE_CASE_INSENSITIVE}, `BCDD`, []Match{}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, []ReFlag{RE_CASE_INSENSITIVE}, `reffgz`, []Match{[]Group{{1, 6}, {1, 6}}}},
+	{`(((((((((a)))))))))`, []ReFlag{RE_CASE_INSENSITIVE}, `A`, []Match{[]Group{{0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}}}},
+	{`(((((((((a)))))))))\41`, []ReFlag{RE_CASE_INSENSITIVE}, `A`, []Match{[]Group{{0, 2}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}}}},
+	{`(.*)c(.*)`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDE`, []Match{[]Group{{0, 5}, {0, 2}, {3, 5}}}},
+	{`\((.*), (.*)\)`, []ReFlag{RE_CASE_INSENSITIVE}, `(A, B)`, []Match{[]Group{{0, 6}, {1, 2}, {4, 5}}}},
+	{`(a)(b)c|ab`, []ReFlag{RE_CASE_INSENSITIVE}, `AB`, []Match{[]Group{{0, 2}}}},
+	{`(a)+x`, []ReFlag{RE_CASE_INSENSITIVE}, `AAAX`, []Match{[]Group{{0, 4}, {2, 3}}}},
+	{`([ac])+x`, []ReFlag{RE_CASE_INSENSITIVE}, `AACX`, []Match{[]Group{{0, 4}, {2, 3}}}},
+	{`([^/]*/)*sub1/`, []ReFlag{RE_CASE_INSENSITIVE}, `D:MSGS/TDIR/SUB1/TRIAL/AWAY.CPP`, []Match{[]Group{{0, 17}, {7, 12}}}},
+	{`([^.]*)\.([^:]*):[T ]+(.*)`, []ReFlag{RE_CASE_INSENSITIVE}, `TRACK1.TITLE:TBLAH BLAH BLAH`, []Match{[]Group{{0, 28}, {0, 6}, {7, 12}, {14, 28}}}},
+	{`([^N]*N)+`, []ReFlag{RE_CASE_INSENSITIVE}, `ABNNXYZN`, []Match{[]Group{{0, 8}, {4, 8}}}},
+	{`([^N]*N)+`, []ReFlag{RE_CASE_INSENSITIVE}, `ABNNXYZ`, []Match{[]Group{{0, 4}, {3, 4}}}},
+	{`([abc]*)x`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCX`, []Match{[]Group{{0, 4}, {0, 3}}}},
+	{`([abc]*)x`, []ReFlag{RE_CASE_INSENSITIVE}, `ABC`, []Match{}},
+	{`([xyz]*)x`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCX`, []Match{[]Group{{3, 4}, {3, 3}}}},
+	{`(a)+b|aac`, []ReFlag{RE_CASE_INSENSITIVE}, `AAC`, []Match{[]Group{{0, 3}}}},
+	{`([abc])*d`, []ReFlag{RE_CASE_INSENSITIVE}, `ABBBCD`, []Match{[]Group{{0, 6}, {4, 5}}}},
+	{`([abc])*bcd`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCD`, []Match{[]Group{{0, 4}, {0, 1}}}},
+	{`^(ab|cd)e`, []ReFlag{RE_CASE_INSENSITIVE}, `ABCDE`, []Match{}},
 }
 
 func TestFindAllMatches(t *testing.T) {