In order to investigate whether high fibrinogen levels were associated with elevated thrombin activity, we measured fibrinogen and fibrinopeptide A in 37 elderly healthy subjects ranging from 60 to 93 years. Fibrinogen levels (519.1 ± 127.0 mg/dl) and fibrinopeptide A (5.9, 0.9–18.1 ng/ml) were significantly higher than in younger controls. A highly significant negative linear correlation was found between fibrinogen and fibrinopeptide A in the elderly subjects (p < 0.01). However, a polynomial regression showed that this negative relationship was present at the fibrinogen levels ranging between 420 and 700 mg/dl. Our results suggest that high fibrinogen levels in elderly subjects do not necessarily mean that their thrombin activity is concomitantly increas