The incidence of complete atrioventricular block (AVB) in a large group of patients with Q-wave inferior acute myocardial infarction (AMI) was 251 (11%) of 2273 patients. This incidence was significantly higher in women (14%) and patients > 70 years old (15%) than in men and patients < 70 years old (10% and 9%, respectively). Patients with complete AVB exhibited more serious arrhythmic and mechanical complications during hospitalization and included more patients with very high enzyme levels than their counterparts without AVB. The in-hospital mortality rate was 92 (37%) of 251 patients with complete AVB versus 200 (11%) of 1890 in those without AVB (p < 0.0001). After adjustment for age, gender, and important anamnestic, medical, and enzymatic findings, complete AVB emerged as an independent predictor of in-hospital mortality, yielding an odds ratio of 2.0 (90% confidence interval 1.12 to 3.57). The long-term (5-year) mortality rate in hospital survivors was slightly but not significantly higher in patients with complete AVB (28%) during hospitalization than in their counterparts with no AVB (23%). In view of these data, patients with inferior AMI in whom complete AVB develops are at increased risk and may benefit from urgent revascularization; the postdischarge management of survivors with complete AVB should be no different from that of patients without AVB.