Prevention of restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains a major challenge. To determine whether lovastatin could prevent restenosis, between December 1987 and July 1988, a total of 157 patients undergoing successful PTCA were randomly and prospectively assigned to the lovastatin group or a control group. Seventy-nine patients received lovastatin (20 mg daily if the serum cholesterol level was less than 300 mg/dl and 40 mg daily if the serum cholesterol level was greater than or equal to 300 mg/dl) in addition to conventional therapy (lovastatin group). Seventy-eight patients received conventional therapy alone (control group). Fifty patients in the lovastatin group and 29 in the control group were evaluated with coronary angiography at an interval of 2 to 10 months (mean 4 months). The restenosis rate was evaluated according to the number of patients showing restenosis, the number of vessels restenosed, and the number of PTCA sites restenosed. Restenosis was defined as the presence of greater than 50% stenosis of the PTCA site. In the lovastatin group 6 of 50 patients (12%) had restenosis compared with 13 of 29 patients (44.4%) in the control group (p less than 0.001). When the number of vessels restenosed was considered, only 9 of 72 vessels (12.5%) restenosed in the lovastatin group compared with 13 of 34 vessels (38.2%) in the control group (p less than 0.002). Similarly, 10 of 80 (12.5%) PTCA sites restenosed in the lovastatin group compared with 15 of 36 (41.7%) in the control group (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)