The study had a prospective case-control design. Medical records of possible cases of idiopathic dilated cardiomyopathy who were discharged from five Washington, D. C. acute care hospitals over a two year period were abstracted so that standard diagnostic criteria could be applied. Two neighborhood controls were identified for each case. Cases and controls were matched on five year age intervals, sex, and telephone exchange. Cases were contacted annually during the two to three year follow-up period to determine vital status. The study determined whether the reported association between idiopathic dilated cardiomyopathy and asthma could be confirmed and the possible role of asthma medications, cigarette smoking, moderate alcohol consumption, and diabetes mellitus in the etiology of idiopathic dilated cardiomyopathy. The role of hypertension was also studied.. Statistical analysis consisted of case-control comparisons using conditional logistic regression techniques, and survival analyses using Kaplan-Meier curves and proportional hazards models.