To determine if morphology of procedure-associated dissections could help predict clinical outcome, angiograms of 691 coronary artery dissections resulting from percutaneous transluminal coronary angioplasty were categorized according to the National Heart, Lung, and Blood Institute classification system. Classes of dissection were then correlated with clinical outcome: 543 patients with type B dissections had no increase in morbidity and mortality when compared with patients without dissection, with a similar success rate of 93.7%. Complications in this group were low and compared favorably with complication rates in procedures not associated with dissection. One hundred forty-eight procedures associated with dissections of types C to F had a significant increase in in-hospital complications, including acute closure (31%), need for emergency coronary bypass surgery (37%), myocardial infarction (13%) and repeat angioplasty (24%). The overall clinical success rate for those with types C to F dissection was 38%. The differences in clinical success and acute complications between type B and types C to F dissections were statistically significant at p less than 0.0005 for all variables studied. The angiographic morphology of a dissection during coronary angioplasty can predict clinical outcome, aiding in selection of effective therapy.