Contrasting data have been reported about cardiovascular diseases in psoriatic patients. The aim of this study was therefore to evaluate blood coagulation and fibrinolysis in psoriatic patients. For this purpose, in a first group of 48 patients, we measured blood coagulation and fibrinolysis inhibitors [antithrombin III (AT), protein C (PC) and alpha 2-antiplasmin (AP)], the products of thrombin and plasmin activity [fibrinopeptide A (FpA) and B beta(15-42) (B beta)], plasminogen (PLG) and fibrinogen (FBG). When all patients were considered we found a significant increase in B beta and FpA levels, while PC, PLG and AP values were significantly decreased when compared to controls. FBG and AT were not different from the controls. In order to understand whether the observed abnormalities of blood coagulation and fibrinolysis were related only to psoriasis we divided all the patients into two groups: (1) patients with cardiovascular disease or other risk factors (n = 28) and (2) patients affected only by psoriasis (n = 20). Since no difference was observed between groups 1 and 2, we conclude that these findings are related to psoriasis. Subsequently we considered a different group of psoriatic patients. In these patients we measured FpA and two new thrombin activation indicators, such as prothrombin fragment 1 + 2 and thrombin-antithrombin complex (TAT). In addition we evaluated the levels of D-dimer, the product of the dissolution of cross-linking fibrin by plasmin. In this second group FpA, prothrombin fragment 1 + 2 and D-dimer were significantly higher than controls. Only TAT was not statistically different from those of the controls.(ABSTRACT TRUNCATED AT 250 WORDS)