OBJECTIVE: To investigate the relationship between fasting insulin concentrations and several metabolic and anthropometric variables in the Mexico City population. DESIGN: Cross-sectional, randomized, stratified by age, sex and economically active and inactive. SUBJECTS: 700 healthy adults, older than 20 years, 396 males and 304 females. MEASUREMENTS: Body mass index, waist to hip ratio, systolic and diastolic blood pressure, insulin, glucose, triglycerides, total, HDL and LDL cholesterol and lipoprotein(a). RESULTS: Means for age were 39 +/- 13 years for men and 41 +/- 12 for women (p < 0.05). In males, the mean values of body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, triglycerides, glucose and LDL-cholesterol : HDL-cholesterol increased significantly with higher insulin levels. A significant inverse tendency was observed for the mean concentrations of HDL-cholesterol and lipoprotein(a). Age, total cholesterol and LDL-cholesterol were not related to the insulin levels. A similar pattern was observed in women, significance, however, was only obtained for the body mass index, triglycerides, glucose, HDL-cholesterol and lipoprotein(a). Age-adjusted multiple regression analysis showed that insulin was directly and independently associated to triglyceride levels and inversely with lipoprotein(a) concentrations for both sexes, and with HDL-C, only in males. CONCLUSIONS: The prevalence of insulin resistance related metabolic disorders was high in a random sample of the Mexico City population. Increased cardiovascular risk factors associated with the insulin resistance syndrome were observed with higher insulin levels, and lipoprotein(a) was inversely and significantly related to insulin. Preventive strategies are urgently needed to avoid the already increased incidence of morbidity and mortality associated to atherosclerotic disease.