To elucidate the role of hypertension as part of the insulin resistance syndrome, the longitudinal relationships of hypertension and overweight with hyperinsulinaemia and glucose tolerance were examined in the Dutch and Finnish cohorts of the Seven Countries Study (Zutphen, and east and west Finland). Three cohorts of men, born between 1900 and 1919, were first examined in 1959/1960. At the 30-year follow-up survey a 2-h glucose tolerance test was carried out on 619 of the surviving men, and fasting insulin was also measured. Blood pressure and body mass index (BMI) were measured several times during the entire 30-year follow-up period. In cross-sectional analyses, men with diabetes and impaired glucose tolerance at the 30-year follow-up examination had a significantly higher systolic blood pressure and a higher prevalence of hypertension than men with normal glucose tolerance, independent of age, cohort and BMI (p < 0.01). These differences had already been seen 5, 20 and 30 years earlier. Subjects with hyperinsulinaemia (fasting insulin > or = 9.2 mU/l) had a higher BMI and a higher prevalence of hypertension. This cross-sectional association with hypertension was independent of age, cohort and BMI. BMI levels of men with hyperinsulinaemia had been shown to be higher 5, 20 and 30 years earlier, but blood pressure levels had not. These results indicate that hypertension is independently associated with glucose tolerance and insulin resistance in three Caucasian cohorts. Changes in blood pressure precede abnormal glucose tolerance but not hyperinsulinaemia; therefore, glucose tolerance appears to be a stronger correlate of hypertension than hyperinsulinaemia.