Summary: A cytochrome P450 1A2 (CYP1A2) polymorphism interacted with coffee intake on myocardial infarction. Coffee was associated with an increased risk only among individuals with slow caffeine metabolism. For individuals younger than the median age of 59 years, the ORs (95% CIs) associated with consuming less than 1, 1, 2–3, or 4 or more cups of coffee per day were 1.00, 1.24 (0.71–2.18), 1.67 (1.08–2.60), and 2.33 (1.39–3.89), respectively, among carriers of the *1F allele. The corresponding ORs (95% CIs) for those with the *1A/*1A genotype were 1.00, 0.48 (0.26–0.87), 0.57 (0.35–0.95), and 0.83 (0.46–1.51).