The present study investigated the association between 24-h urinary sodium excretion and heart rate in the determination of blood pressure (BP) levels in a large random population sample from eastern Finland. Three independent risk factor surveys were performed in 1979, 1982 and 1987 using the same methodology. Data from each survey was pooled for subjects aged 25-64 years who reported a complete 24-h urine collection and were not on the current antihypertensive treatment (1640 men and 1686 women). The effect of urinary sodium excretion and heart rate was examined by regressing BP on urinary sodium excretion and pulse rate, together with age and body mass index (BMI). Analyses stratified by quintiles of heart rate were also performed. There was no association between urinary sodium and BP either in men or in women. There was a significant correlation between heart rate and both systolic and diastolic BP in both men and women. A significant interaction between age and BMI with heart rate was also found in both sexes. Interaction between urinary sodium and heart rate was found neither in men nor in women. Among men, after adjustment for age and BMI, there was a curvilinear relation between 24-h urinary excretion of sodium and diastolic BP (P = 0.054) in the lowest quintile of heart rate (<60 beats/min). No correlations were observed among women in any of the quintiles of heart rate.