BACKGROUND Trapidil is an antiplatelet drug with specific platelet-derived growth factor antagonism and antiproliferative effects in the rat and rabbit models after balloon angioplasty. RESULTS The Studio Trapidil versus Aspirin nella Restenosi Coronarica (STARC) is a multicentric, randomized, double-blind trial to assess the effects of trapidil in angiographic restenosis prevention after percutaneous transluminal coronary angioplasty (PTCA). Patients received either trapidil 100 mg TID or aspirin at the same dosage at least 3 days before angioplasty and for 6 months thereafter. Coronary angiograms before PTCA, after PTCA, and at 6-month follow-up were quantitatively analyzed with manual calipers. Of the initial 384 patients recruited, 254 were evaluable for restenosis analysis (128 trapidil, 126 aspirin). Restenosis, defined as a loss of initial percent gain after PTCA of at least 50% (primary end point), occurred in 24.2% of the trapidil group and 39.7% of the aspirin group (P < .01). A similar result was obtained when restenosis per vessel was considered (trapidil, 23.3%; aspirin, 36.9%; P = .018). Clinical events at follow-up were similar in the two groups except that recurrent angina was significantly more frequent in the aspirin group, 43.7% versus 25.8% in the trapidil group (P < .01). Trapidil was well tolerated: only 6 patients had to discontinue the drug because of side effects, which was not different from the aspirin group. CONCLUSIONS Trapidil reduces restenosis after PTCA at the dosage of 100 mg TID and favorably influences the clinical outcome thereafter.