Angiographic evidence of coronary dissection after angioplasty is found in 25% to 30% of cases. Although patients are usually asymptomatic, in a small percentage angioplasty-induced coronary dissection results in luminal impairment and ischemic complications. The present study was undertaken to identify factors responsible for a predisposition to coronary dissection after angioplasty and to determine whether major and minor dissections share the same underlying risk factors. Clinical records and angiograms from 363 patients with 489 lesions were retrospectively graded for the presence and severity of dissection and complications. Both major and minor angiographic dissections were noted in 30.3%, and in 8.8% they were major. On multivariate analysis the most significant correlates of any dissection included a balloon-to-artery ratio > 1.1 (p = 0.0001), calcification (p = 0.003), presence of other lesions in the angioplasty vessel (p = 0.018), and lesion length (p = 0.02). However, in a multivariate model there were no variables that could predict whether a dissection would be major or minor. Only the mean total number of inflations was significantly different, but this was likely the result rather than the cause of dissection. Thus a number of variables can predict the occurrence of angiographic coronary dissection after angioplasty. Major dissections constitute a small fraction of the total number but are difficult to predict differentially.