In this association study the authors compared the insertion/deletion (I/D) angiotensin-I converting enzyme (ACE) gene polymorphism in females and males with premature myocardial infarction (MI). I/D ACE gene polymorphism was tested in 738 subjects: 302 patients with MI (151 men and 151 women) and 436 healthy subjects (207 men and 229 women). In women the ACE-DD genotype was not associated with MI (OR 1.1, 95% CI 0.6-2.1, p=0.6), whereas the ACE-DD genotype conferred a 2-fold independent risk for MI in men (95% CI=1.2-3.4; p=0.013) after adjustment for cardiovascular risk factors. The authors found evidence for the sex difference in the effect of the ACE-DD genotype on MI risk. The ACE-DD genotype conferred a 2-fold independent risk for premature MI in males.