Of 124 consecutive patients undergoing elective excimer laser coronary angioplasty, 33 (26%) had periprocedural occlusion following excimer laser irradiation. Successful management (reopened vessel, no death, no myocardial infarction, no emergency bypass surgery) including repeat lasing, subsequent percutaneous transluminal coronary angioplasty, use of intracoronary nitroglycerin or streptokinase was achieved in 32 of the patients with acute occlusion following excimer laser coronary angioplasty. In one patient a nonfatal anterior myocardial infarction occurred. A late event occurred in two patients despite patency at the control angiography 24 h later. Multiple logistic regression modeling was used to examine the relationship between various characteristics and the risk of acute vessel closure. The preprocedural and procedural variables analyzed included progressive spasm prior to occlusion and lesion morphology after intervention (angiographic complications after percutaneous transluminal coronary angioplasty were prospectively divided into class 0, no complication, and classes 1-3, according to purely descriptive morphological characteristics). These showed a multivariate correlation with acute occlusion during excimer laser coronary angioplasty. These results suggest that acute vessel closure during stand-alone excimer laser coronary angioplasty is a benign but unpredictable event.