The correlation between overweight and the climacteric was studied in 550 menopause clinic patients by investigating certain clinical and sociocultural parameters (age, marital status, educational level, occupation and type of work, calorie intake, smoking habits, parity, blood pressure, previous hormonal therapy and climacteric symptoms), evaluating plasma levels of various hormones (17β-oestradiol, follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone, hydrocortisone, adrenocorticotrophic hormone (ACTH), triiodothyronine (T3), thyroxine (T4), growth hormone (GH) and insulin), glucose and various lipid fractions (total lipids, total cholesterol, nonesterified fatty acids (NEFA), triglycerides and phospholipids) and exploring the blood-clotting pattern (Owren's test, euglobulin lysis time, antithrombin III and prothrombin agglutination time (PAT). The subjects were classified as normal weight or overweight by reference to Broca's Index, as modified by Brusch, and the degree of overweight was determined by means of the Body Mass Index (BMI). Of the subjects examined, 49% were overweight and, in successive years following the menopause, there was a growing bipolarization of the weight increase. The correlation between overweight in the climacteric and the parameters considered was found to be significant only in regard to calorie intake, age and educational level. Post-menopausal gonadotrophin levels in blood were significantly lower in the overweight than in the normal-weight women. With the onset of menopause, the plasma level of testosterone fell in the normal-weight women, while it increased, along with that of hydrocortisone, in the overweight women. In the normal-weight women at menopause, it was found that there was a tendency towards a substantial increase in lipid fractions and glycaemia, as well as a state of hypercoagulability. In the overweight women, the tendency was towards an even more marked increase in both glycaemia and the various lipid fractions, and, besides the usual hypercoagulative state, there was an associated reduction in fibrinolytic activity. It is concluded that the menopause not only causes metabolic changes but also aggravates the metabolic and endocrine tendencies which characterize overweight subjects and thus, clinically, constitutes an obesity risk factor in those women who already demonstrate a tendency towards overweight in the pre-menopausal phase.