The study aimed to evaluate the behaviour of two pre-thrombotic markers (hyperfibrinogenemia and hypoanti-thrombinemia) in obesity which is considered a factor of atherogenous risk. Ninety-three obese subjects were included in the study (29 M, 64 F, mean age 55 +/- 6, BMI 33 +/- 1), including 62 Type 2 diabetics. The following were assayed in each subject: glucose, total cholesterol, triglycerides (enzymatic method), fibrinogen (coagulometric method) and anti-thrombin III (chromogenic method). Results were assessed in relation to sex, age (0-50, 51-65, over 65), BMI (upto 30, 31-35, over 35), waist/hip ratio (upto 0.95, 0.96-1.02, over 1.02), cholesterolemia (upto 200, 201-250, over 250 mg%) and triglyceridemia (upto 150, 151-200, over 200 mg%). A significant increase (0.05) in fibrinogenemia was observed in the subjects aged between 51-65, with BMI above 35, with an intermediate waist/hip ratio (0.96-1.02) and with cholesterolemia over 250 mg%; reduced values of anti-thrombin III were found in subjects over 65 years old and with the lowest waist-hip ratio (upto 0.95); no significant data were obtained for the other parameters and for the correlation between fibrinogen and anti-thrombin III. The pro-thrombotic importance of hyperfibrinogenemia is underlined in obese subjects; this is proportional to age, to the degree of overweight and levels of cholesterolemia, even if equivocal results emerge with regard to the "android" variety. The reduction of anti-thrombin III is correlated to senility and, surprisingly, to the gynoid-type waist/hip ratio.(ABSTRACT TRUNCATED AT 250 WORDS)