A community-wide study of patients hospitalized with acute myocardial infarction in metropolitan Baltimore was conducted to examine socio-demographic and clinical characteristics in association with ventricular fibrillation and cardiac arrest (VF/CA). Multivariate analyses revealed that variables significantly associated with occurrence of VF/CA included older age (60 years or older), male sex, and a history of cigarette smoking. These factors allow the identification of subgroups of patients hospitalized with acute myocardial infarction at high risk for the subsequent development of VF/CA, in whom prophylactic therapy and close surveillance are especially recommended.