In order to investigate whether α2-antiplasmin (α2-AP) levels may be related to thrombin activity, we measured α2-AP and fibrinopeptide A (FPA) in 51 patients with clinical conditions frequently associated with increased thrombin activity. The diagnoses were: atherosclerotic disease, chronic inflammatory disease and hematological neoplastic disease. A significant negative correlation was found between α2-AP and FPA (p < 0.01). When patients were divided into three subgroups on the basis of their FPA levels, a significant reduction in α2 9 ng/ml). Accordingly, a significant negative relationship between α2-AP and FPA was found only in this subgroup (p < 0.01). Our data suggest that the partial consumption of α2-AP in patients with elevated FPA levels may reflect a subclinical fibrinolysis activation secondary to increased thrombin ac