It has been shown that myocardial infarction survivors are more likely to carry an insertion/deletion polymorphism (I/D) of the angiotensin-converting-enzyme (ACE) gene than age-matched population controls. To test whether the association with coronary risk had been under-estimated, the frequency of the ACE I/D was studied in 213 fatal cases of definite and possible myocardial infarction which came to autopsy in the Belfast MONICA Project area. In comparison to controls from the same population, the autopsy cases had an increased frequency of the ACE D allele (p < 0.02). The overall odds ratios were 2.2 for DD vs. II, and 1.8 for ID vs II (test for trend p = 0.01). The findings bear out the hypothesis that the ACE I/D polymorphism is a risk factor for fatal myocardial infarction and sudden cardiac death.