OBJECTIVE Proliferation of vascular smooth muscle cells is a major event in atherogenesis. Several growth factors have been well documented to control this proliferation. Inhibition by suramin of the binding of some growth factors to their receptors has recently been reported. The aim of this study was to examine the effects of this agent on neointimal thickening following intimal mechanical injury, as well as on platelet function. METHODS Intimal thickening was induced by indwelling of polyethylene tubing for 24 h in the rabbit aorta. Rabbits were killed 10 d after drawing out the tubing. Throughout the experiment, suramin (15 mg.kg-1) was injected intravenously every 24 h. Morphological and morphometrical studies were performed in the suramin treated group (n = 6) and in a control group (n = 6). Platelet-rich plasma was prepared from animals before and 3 h after injection of suramin. Platelet aggregation and ATP release induced by collagen were examined. Platelet adhesion on the de-endothelialised area of the rabbit aorta was also examined in the two groups. RESULTS The mean intimal thickening in the suramin treated group was significantly less than in the control group. Smooth muscle cell replication and cell density in the thickened intima of the suramin treated group were less than in control. Suramin did not affect collagen induced platelet aggregation, ATP release, or platelet adhesion. CONCLUSIONS Suramin has an inhibitory effect on the neointimal thickening and intimal smooth muscle cell proliferation after intimal injury in the rabbit aorta, but has no effect on platelet function.