The clinical significance of the angiographic no-reflow phenomenon was evaluated in 93 patients with acute myocardial infarction treated by percutaneous transluminal coronary angioplasty (PTCA). On the basis of the post-PTCA angiograms, patients were divided into three groups: normal angiogram (group 1, n = 65), slight no-reflow (group 2, n = 13), and severe no-reflow (group 3, n = 15). Regional wall motion in the chronic phase was depressed in groups 2 and 3 compared with group 1. The proportion of the area of the transmural infarction to that of the total infarction determined by scintigraphy was higher in groups 2 and 3 than in group 1. A significantly higher incidence of myocardial rupture and of death resulting from cardiac causes was observed in group 3 compared with group 1. The severity of this phenomenon immediately after an emergency PTCA correlated well with the severity of myocardial damage, with patients having severe no-reflow showing the poorest prognosis.