The pharmacologic profile of the angiotensin-converting enzyme inhibitor, captopril, is described. After reviewing the total clinical experience of captopril from the world literature and manufacturer's files, a small subgroup of clinically complex patients at particular risk of side effects and in whom the drug must be used with caution is characterized. Evidence is available that demonstrates that lower doses (150 mg/day or less, with modest doses of diluretic agents) are effective in both short- and long-term therapy, while the incidence of side effects is substantially reduced. With this background information, the benefit-risk ratio is substantially improved and the use of captopril as a primary agent in the management of hypertension may be considered.