This review will discuss the safety profiles of the angiotensin-converting enzyme (ACE) inhibitors captopril, enalapril and lisinopril in patients with hypertension. In general, the safety profiles of ACE inhibitors compare favourably with those of other agents used for the treatment of hypertension. Adverse effects are not common when ACE inhibitors are used at the currently recommended doses. The adverse experiences that do occur with ACE inhibitors can be divided into 3 categories. Hypotension, hyperkalaemia and renal impairment are related directly to the blockade of the angiotensin-converting enzyme. Attention to the clinical condition, including concomitant therapy, reduces the risk of these adverse effects of ACE inhibition. Other adverse effects such as cough and angioedema also occur with all ACE inhibitors. The mechanisms are poorly understood, making it difficult to predict in which patients they will occur. Adverse effects such as rash, dysgeusia, neutropenia and proteinuria, which were reported relatively frequently in the early experience with captopril, are reported less frequently with lower doses of captopril and do not appear to be a problem with other ACE inhibitors such as enalapril and lisinopril.