Restenosis continues to be the most important limitation of percutaneous transluminal coronary angioplasty (PTCA). Many clinical, angiographic, and procedural variables are thought to be related to the development of restenosis. This study was aimed at investigating the effects of no dissection, minor dissections, and major dissections on the long-term outcome of lesions after successful PTCA. The study group comprised 91 patients with 100 lesions who underwent successful PTCA and in whom follow-up coronary angiography was performed at 8.8 +/- 7.2 (two to twenty-three) months after dilation. Dissections were classified according to the National Heart, Lung, and Blood Institute criteria. Restenosis was defined as more than 50% stenosis at follow-up angiography. Restenosis rates were found to be 22% in the no-dissection group (10 restenoses in 46 patients), 27% in the minor dissection group (11 restenoses in 40 patients), and 36% in the major dissection group (5 restenoses in 14 patients). The authors applied corrected Yates Chi-square test and no difference was observed in the restenosis rate between the group without any dissections and that with minor dissections (P > 0.05). However, a statistically significant difference was observed in the restenosis rate between the major dissection group and the other two groups (P < 0.05). The authors conclude that the occurrence of major dissections after successful PTCA may adversely affect the long-term outcome and may increase the restenosis rate.