Abrupt vessel closure of the dilated vessel continues to represent a significant limitation of coronary angioplasty. Despite increasing operator experience and improved technology, abrupt vessel closure continues to represent the most important complication of balloon angioplasty. Intracoronary stent implantation and pharmaceutical blockade of the GPIIb/IIIa receptor serve as effective tools in the prevention of abrupt vessel closure without completely resolving this problem. About 50% of patients presenting with abrupt vessel closure exhibit additional complications including myocardial infarction, necessity of CABG or death occurring in up to 10% of acute occlusions. The purpose of this study is to evaluate if quantitative coronary angiography and assessment of clinical and laboratory data allows risk stratification concerning the probability of abrupt vessel closure. PTCA in the setting of acute coronary syndrome is associated with a markedly increased risk of abrupt vessel closure, indicating that different risk factors may contribute to the development of abrupt vessel closure in patients presenting with stable angina or acute coronary insufficiency syndromes. 798 uncomplicated PTCA procedures for stable angina pectoris were compared with 68 interventions that were complicated by abrupt vessel closure. Furthermore, 133 successful angioplasty procedures for acute coronary syndromes defined as acute myocardial infarction or unstable angina pectoris were matched with 31 procedures for acute coronary syndromes with consecutive abrupt vessel closure. In patients presenting with stable angina pectoris stenosis length, stenosis eccentricity, minimal lumen diameter, degree of the stenosis after angioplasty, female gender, and fibrinogen could be defined as independent predictors of abrupt vessel closure. In acute coronary syndromes, only minimal lumen diameter, recanalization of completely occluded coronary arteries and fibrinogen were associated with an increased risk of abrupt vessel closure.