The results of coronary angioplasty of chronic total occlusions are still controversial. We examined baseline clinical and angiographic parameters and the success and complication rates of 142 consecutive procedures of coronary angioplasty of chronic occlusions selected among 1084 total procedures performed between January 1989 and May 1993. Procedural success was obtained in 109 procedures (77%) with 4 major cardiac complications (2.8%) consisting in one cardiac death caused by left main artery occlusion following an attempt of dilatation of an occluded left anterior descending artery, two non Q wave myocardial infarctions caused by distal embolization and one cardiac tamponade following artery perforation, successfully treated by pericardiocentesis. Extensive coronary dissection occurred in 24 procedures (17%): 5 caused vessel reocclusion and 19 were successfully treated by prolonged balloon inflation and/or use of long balloons or stent implantation. Among 15 baseline clinical and angiographic variables, none was predictive of cardiac complications or coronary artery dissection. In contrast, procedural success was significantly related with absence of bridging collaterals, duration of occlusion < 3 months and a tapered or thrombotic morphology of occlusion. Presence or absence of collaterals was the most significant variable selected by multivariate discriminant analysis. When patients with bridging collaterals were excluded from the analysis, occlusion morphology was the most important determinant. Success rates were 95% and 82% in patients with a tapered morphology lesion with < 3 months and > 3 months duration, respectively (ns); in contrast, success rates were 79% and 36% in patients with abrupt occlusion morphology of < and > 3 months duration (p = 0.001).