Abstract: AIM: To investigate the effects of probucol on intimal hyperplasia after balloon injury of carotid artery in rats and the impossible mechanism. METHODS: Forty-five male SD rats were randomly divided into sham-operated group, control group and therapy group. Rat left common carotid arteries were subjected to balloon injury in the control group and therapy group and probucol was administered IG to the therapy group. Arteries of the rats were harvested at 7, 14 and 35 days after balloon injury for immunohistochemical staining and H/E staining. Plasma MDA and SOD levels were detected by radioimmunoassay. Evans blue staining was used to measure the reendothelialized area and immunostaining of proliferating cell nuclear antigen (PCNA) was used to confirm the hyperplastic cells. Neointima thickening was assessed by intima to media area ratio (I/M) using a computer-based Image-Pro plus morphometric system. RESULTS: Compared with those in control group, MDA content decreased and SOD activity increased obviously in the therapy group. Probucol did not inhibit the reendothelialization in the injured carotid arteries as determined by Evans blue staining. PCNA-positive cell index in the intima and media at day 14 after therapy was markedly reduced in the therapy group compared with that in the control group. The area of intima and intima to media area ratio (I/M) on day 35 after balloon angioplasty was markedly attenuated in the therapy group compared with that in control group（0.74±0.11 vs. 1.98±0.53, P<0.01). Probucol reduced I/M by 62.63%. CONCLUSION: Probucol can increase plasma SOD level and reduce MDA level and inhibit vascular smooth muscle cell proliferation and neointimal formation after balloon injury of carotid artery, thus preventing restenosis after angioplasty in rats.