Angiotensin-converting enzyme (ACE) inhibitors are being increasingly prescribed for the treatment of hypertension and heart failure. Not only are they efficacious but the incidence of serious adverse events with ACE inhibitors is similar to that with placebo. ‘First-dose hypotension’ mainly affects the renin-dependent patient. Neutropenia and agranulocytosis have been reported rarely for the nonsulfhydryl compounds. Comparative safety data are provided for captopril, enalapril, and quinapril, a new nonsulfhydryl ACE inhibitor that has been investigated extensively in over 2,000 patients. Results show that the proportion of patients reporting associated adverse events was lower with quinapril (11 %) than with captopril (17%) or enalapril (15%). Similarly, there was a lower proportion of patients withdrawn due to adverse events with quinapril.