Considerable evidence suggests that high plasma concentrations of plasminogen activator inhibitor type 1 (PAI-1) and fibrinogen increase the risk of cardiovascular disease. Recent studies report beneficial effects of dietary fiber on coronary artery disease, although the mechanisms by which high fiber intake reduces the risk of heart disease are not well understood. This study examined the relation of dietary fiber intake to PAI-1 and fibrinogen concentrations in 883 men and 1116 women aged 50.4 +/- 13.8 and 52.1 +/- 13.7 y, respectively, in the National Heart, Lung, and Blood Institute Family Heart Study. Diet was assessed with a semiquantitative food-frequency questionnaire. The natural logarithm was used to transform PAI-1 because of a skewed distribution. In the first through fifth age- and energy-specific quintiles of fiber intake, mean (ln)PAI-1 was 6.09, 5.91, 5.88, 5.82, and 5.67 pmol/L, respectively, for men and 5.50, 5.37, 5.39, 5.23, and 5.18 pmol/L, respectively, for women. Multiple regression showed that when the lowest was compared with the second, third, fourth, and fifth age- and energy-specific quintiles of fiber intake, (ln)PAI-1 was 0.21, 0.25, 0.22, and 0.32 pmol/L lower in men (P for trend = 0.009) and 0.08, 0.06, 0.14, and 0.20 pmol/L lower in women (P for trend = 0.037), respectively, with anthropometric, lifestyle, and metabolic factors adjusted for. No significant association was found between fiber intake and fibrinogen. Waist-hip ratio did not modify the relation of fiber intake to PAI-1 (P for interaction = 0.39 for men and 0.36 for women). These data suggest that higher fiber intake is inversely associated with PAI-1, but not with fibrinogen concentration.