Recently, we provided in vitro and in vivo evidence that several vastatins with different potencies decrease arterial smooth-muscle cell (SMC) proliferation independently of their hypocholesterolemic properties. In this study, the in vivo dose-dependent antiproliferative activity of fluvastatin on neointimal formation induced by the insertion of a collar around one carotid artery was investigated in normocholesterolemic rabbits (five animals per treatment group). Intraperitoneal fluvastatin treatment progressively inhibited intimal to medial tissue ratios (I/M) by 5, 48, and 64% versus controls at doses of 3, 5, or 10 mg/kg/day, respectively. Local arterial delivery by an Alzet pump of mevalonate (8 mg/kg/day) at the site of collar placement fully prevented a fluvastatin (5 mg/kg/day) inhibitory effect on both I/M and SMC proliferation, as assessed by direct incorporation of bromodeoxyuridine (BrdU) into replicating DNA. The results suggest that vastatins exert a direct antiproliferative effect on intimal myocytes beyond their effects on plasma lipids, probably through local inhibition of isoprenoid biosynthesis.