Twenty eight adults, 12 men and 16 women, participated in a 1-yr study designed to assess accurately daily nutrient intake. All subjects lived at home, consumed self-chosen diets, and maintained a detailed daily dietary record throughout the year. Four times during the year blood pressure was measured. Mean daily sodium and potassium intake was calculated for each subject for the 7-day period before blood pressure measurements. Dietary intakes averaged 3.9 and 2.6 g/day of sodium and 3.3 and 2.2 g/day of potassium for men and women, respectively. Mean blood pressures for the four measurements were 120 mm Hg (systolic) and 77 mm Hg (diastolic) for men and 110 mm Hg (systolic) and 70 mm Hg (diastolic) for women. There were no significant correlations between absolute sodium or potassium intake and blood pressure. However, an individual's variability about his own mean potassium intake was significantly negatively correlated to the variability about his own mean systolic pressure in the male subjects (r = -0.43, p less than 0.002). There was no similar correlation in the female subjects. Changes in sodium intake were not associated with changes in blood pressure in either the men or women.