The aim of this study is to investigate the influence of the E4 allele of apolipoprotein E (apo E) on restenosis after percutaneous transluminal coronary angioplasty (PTCA). The subjects were 171 male patients with more than 75% luminal diameter stenotic lesions of the coronary artery who had undergone an elective initial PTCA. The PTCA was successful in 164 patients, 157 of whom completed a prospective 5 month coronary angiography (CAG) follow up to assess the degree of restenosis after their surgery. Patients with previous coronary artery bypass grafting surgery (CABG), 3 vessel disease, complete obstruction or calcified lesions of the coronary artery, cerebro-vascular disease (CVD), arteriosclerosis obliterans (ASO), and renal failure with hemodialysis were excluded, leaving 105 patients in the analysis. Subjects carrying the E4 allele (n = 22, Phenotype E4/2 = 2, E4/3 = 19, E4/4 = 1: E4 group) were well matched with non-carriers (n = 83, Phenotype E2/2 = 0, E3/2 = 4, E3/3 = 79: E3 group) for clinical, and pre-and post-PTCA angiographic features. The restenosis rates were significantly higher in the E4 group than in the E3 group (patient restenosis rate : 59.1 vs 33.7% p < 0.05, lesion restenosis rate: 51.8 vs 30.9% p < 0.05). These results suggest that the E4 allele is associated with a higher restenosis rate after PTCA.