Sixty male survivors of acute myocardial infarction in the week after the Chicago blizzard of Jan 15, 1979, were matched by hospital and sex with 60 myocardial infarction survivors from a week without snowfall to determine whether a history of previous heart disease or of cardiac risk factors increased the risk of a postblizzard myocardial infarction. Cases did not differ significantly from control subjects with respect to age, percentage working full time, or percentage with a history of heart disease, hypertension, smoking, diabetes mellitus, obesity, or gout. Hypercholesterolemia was four times as common among cases as among controls.