We obtained information on 107 women younger than 46 years discharged from a hospital with a diagnosis of acute myocardial infarction. In the series there were 17 women aged 39 to 45 years who were otherwise apparently healthy and had had a natural menopause, hysterectomy, or tubal ligation or whose spouse had had a vasectomy. Among them, nine (53%) were taking noncontraceptive estrogens just prior to admission. Among 34 control women, four (12%) were taking estrogens. The relative risk estimate, comparing estrogen users with nonusers, is 7.5, with 90% confidence limits of 2.4 and 24. All but one of the 17 ml subjects were cigarette smokers. While this illness is rare in most healthy young women, the risk in women older than about 38 years who both smoke and take estrogens appears to be substantial.