Plasma fibrinogen is an independent risk factor for coronary heart disease (CHD) in men; however, its role in women is less clear. We examined the ability of plasma fibrinogen to predict CHD in a community-based, case-control study of women aged 65 years or younger living in the greater Stockholm area. Cases were all patients hospitalized for an acute coronary event between February 1991 and February 1994. Controls were randomly selected from the city census and were matched to cases by age and catchment area. Plasma fibrinogen was measured 3 to 6 months after hospitalization by using a fibrinogen assay based on fibrinogen polymerization time measurement. Of the 292 consecutive cases, 110 (37%) were hospitalized for an acute myocardial infarction and 182 (63%) for angina pectoris. The mean age+/-SD in both patients and controls was 56+/-7 years. Mean levels of plasma fibrinogen in patients and controls were 3.66+/-0.81 and 3.25+/-0.64 g/L (P<0.0001), respectively. The age-adjusted odds ratio (OR) for CHD in the highest versus the lowest quartile of plasma fibrinogen was 6.0 (95% confidence interval [CI], 3.5 to 10.4). After adjustment for age, cigarette smoking, body mass index, systolic blood pressure, total cholesterol, high density lipoprotein cholesterol, triglycerides, and educational level, the OR was 3.0 (95% CI, 1.6 to 5.5). Further adjustment for C-reactive protein yielded the same result. In both premenopausal and postmenopausal women, the multivariate-adjusted ORs were 7.0 (95% CI, 1.8 to 28.3) and 2.1 (95% CI, 1.0 to 4.4), respectively. These results provide evidence that plasma fibrinogen is associated with an excess risk of CHD in women.