Restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains a major problem limiting the clinical efficacy of the procedure. It has been shown that SMC proliferation plays a predominant role in this accelerated atherosclerotic process. In vitro and in vivo experiments with the LMWH reviparin (LU 47311) suggest a pronounced inhibitory effect of this compound on SMC proliferation. To evaluate the safety of reviparin and the incidence of angiographic restenosis in humans a study with increasing dosages was conducted in 41 patients. Repeat coronary angiography was performed 3 months after angioplasty. Restenosis occurred in 5 of 37 evaluable patients (14%) with initially successful PTCA. No major bleeding complication was documented for any of the patients included in this trial. Thus, in this limited series, administration of LU 47311 (reviparin) resulted in a low incidence of restenosis following PTCA without causing major bleeding complications. A randomized trial in a larger population is warranted to define the real impact of this compound for reduction of restenosis in patients who underwent successful balloon angioplasty.