As part of a study of risk factors for coronary heart disease 24 hour urine collections were obtained from 7354 men and women aged 40-59 selected at random from 22 districts throughout Scotland (Scottish heart health study). The mean of two standardised measurements of blood pressure was related to the reported consumption of alcohol and measurements of height, weight, pulse rate, and electrolyte excretion. Several significant correlations were found with both systolic and diastolic pressure, but only the coefficients for age, body mass index, and pulse rate were greater than 0.1. Alcohol consumption showed a weak positive correlation with blood pressure in men. Sodium excretion showed a weak positive correlation with blood pressure in both sexes, and potassium excretion showed weak negative correlations. In multiple regression analysis age, pulse rate, body mass index, alcohol consumption, and potassium excretion had significant independent effects but sodium excretion did not. Although measuring blood pressure twice on one occasion and 24 hour urinary sodium excretion only once may have weakened any potential correlation, the most likely explantation of these results is that the relation between sodium and blood pressure in the population is weak and that potassium and alcohol are of greater importance.