Restenosis remains the principal drawback of percutaneous transluminal coronary angioplasty (PTCA) since 30-35% of patients still experience it 6 months after the intervention. Several studies have clearly demonstrated that restenosis is a complex multifactorial process that involves smooth muscle cell (SMC) migration and proliferation in the intimal layer of the coronary artery. Among others, the platelet-derived growth factor (PDGF) seems to play an important role in this process. That is why researches have been made in finding and developing new agents able to inhibit PDGF. Trapidil (triazolopyrimidine) (T), is a potent PDGF inhibitor that has been efficacious in preventing restenosis after balloon angioplasty in the experimental animal and after PTCA in a limited clinical trial. The Trapidil Restenosis Trial (STARC study) is a double blind randomized trial of T 100 mg t.i.d. vs. Aspirin (ASA) 100 mg t.i.d. 360 patients have been enrolled from April 1990 until May 1992, excluding recent myocardial infarctions, thrombolysis, restenotic and venous graft lesions and 302 have terminated follow-up. This paper describes the clinical background, the protocol and baseline data of the patient population including data regarding initial stenosis and type of vessel treated.