Stent implantation has decreased the incidence of restenosis after coronary intervention, but has not eliminated it. The contribution of the angiotensin-converting enzyme (ACE) genotype to the development of coronary artery disease and restenosis after coronary stenting was investigated in 67 Japanese patients in whom 103 lesions in which stents had been successfully implanted were assessed by quantitative coronary angiography, before, immediately after coronary stenting, and during follow-up. The distribution of the patients with the DD, ID, and II genotypes was 13%, 54%, and 33%, respectively. The prevalence of multivessel disease in the DD genotype was significantly higher (DD genotype: 78%; ID genotype: 58%; II genotype: 27%, chi2=8.13, p=0.016) and the late loss in the DD genotype (1.43+/-0.96 mm) was significantly greater (ID genotype: 0.78+/-0.98 mm and II genotype: 0.79+/-0.88 mm, p<0.05 vs DD genotype). However, there was no significant difference in the restenosis rate among the 3 genotypes. The present study in Japanese patients indicates that the DD genotype is associated with more extensive coronary artery disease and progression of the inward remodeling within the stented lesion, which is primarily caused by neointimal hyperplasia.