Whether angiotensin-converting enzyme (ACE) inhibitors are interchangeable and equally efficacious after acute myocardial infarction (AMI) is controversial. We assessed whether ramipril was superior to other ACE inhibitors after AMI as suggested by a previously published study. We performed a retrospective cohort study using linked administrative databases on >1.4 million elderly residents in the province of Ontario who were admitted to the hospital for AMI, survived >or=30 days after discharge, and were initiated on an ACE inhibitor after AMI and remained on the same ACE inhibitor from April 1, 1997 to March 31, 2000. We followed patients for 2 years and measured readmission for AMI or mortality, together or alone. Our cohort included 5,408 elderly patients. Compared with patients on enalapril, there was no significant difference for the combined end points of readmission for AMI or mortality across users of ramipril (adjusted hazard ratio 0.95, 95% confidence interval 0.79 to 1.15), lisinopril (adjusted hazard ratio 1.02, 95% confidence interval 0.84 to 1.25), or other ACE inhibitors (adjusted hazard ratio 1.08, 95% confidence interval 0.88, 1.32). In conclusion, the findings of this study support a class effect among ACE inhibitors in treatment after AMI.