BACKGROUND: Several angiotensin-converting enzyme inhibitors have antiproliferative effects in a rat model after carotid artery balloon injury. METHODS AND RESULTS: We conducted a randomized, double-blind, placebo-controlled trial to assess the effect of fosinopril, a novel angiotensin-converting enzyme inhibitor, in restenosis prevention after percutaneous transluminal coronary angioplasty (PTCA). Patients received fosinopril or matched placebo 10 mg at least 18 hours before PTCA, 20 mg at least 4 hours before PTCA, and 40 mg daily for 6 months. In addition, all patients received aspirin. Coronary angiograms before PTCA and immediately after PTCA as well as at 6-month follow-up were quantitatively analyzed. A total of 509 patients were recruited. The final per-protocol population consisted of 153 fosinopril-treated and 151 placebo-treated patients. Restenosis rates according to the National Heart, Lung, and Blood Institute criterion 4 (loss of > or = 50% of the initial gain [primary end point]) were 45.7% and 40.7% in the fosinopril and control groups, respectively (not significant). The respective mean differences in minimal coronary luminal diameter between post-PTCA and follow-up angiograms were -0.59 +/- 0.71 mm and -0.51 +/- 0.67 mm (not significant). Clinical events during the 6-month follow-up period, analyzed on an on-treatment basis, were ranked according to the most serious event. The respective numbers in the fosinopril and the control groups were for death, 0 and 0; myocardial infarction, 0 and 0; coronary artery bypass graft surgery, 1 and 3; repeat PTCA, 35 and 35; recurrent signs of ischemia necessitating early repeat coronary angiography and managed medically, 6 and 7; and none of the above, 111 and 106. All these differences were significant. CONCLUSIONS: Administration of fosinopril in a dose of 40 mg daily during 6 months after PTCA does not prevent restenosis and has no effect on overall clinical outcome.