Objective To assess whether apparently healthy subjects with a family history of systemic hypertension have a higher risk of presenting the insulin resistance syndrome. Subjects Three hundred and eighty-six subjects aged 20-65 years. Setting A middle socio-economic class urban community from Mexico City. Method All subjects and, when necessary, their first-degree relatives, answered a questionnaire and underwent a physical examination with measurement of height, weight and blood pressure. Serum insulin, glucose, cholesterol and triglycerides were measured during fasting and 2 h after an oral load of 75 g glucose. Results A family history of systemic hypertension was present for 167 (43%) of the subjects, of whom 123 (31%) were obese. Subjects with a family history of hypertension had higher systolic blood pressures than did those without such a history (120 ± 15 versus 115±10mmHg). In the logistic regression model, the body mass index and age showed statistically significant effects on the fasting glucose: insulin ratio and on serum insulin levels after an oral load of glucose. When men and women were analysed separately, only in men were higher systolic and mean blood pressures and lower glucose: insulin ratios observed. In the logistic regression analysis the body mass index was a significant predictor of the glucose: insulin ratio and serum insulin levels after an oral load of glucose, especially in men. Conclusion Apparently healthy male offspring of hypertensive parents have higher blood pressure levels and lower insulin sensitivities than do offspring of normotensive parents. Insulin resistance was related to obesity, but not to a family history of hypertension, as had previously been reported by other research groups.