Dietary sodium measurement in populations has severe limitations whether assessment is based on urinary excretion or on food intake methods. We have validated a simple instrument to determine total dietary sodium intake of populations in a pilot study of 10 women, 20 to 36 years old. Sodium intake determined by means of the sodium measurement instrument was correlated with sodium intake from food analysis, sodium intake calculated from food composition tables, and measurement of 24-hour urinary sodium excretion. Sodium values obtained with the instrument are based on regression equations, which incorporate information as follows: an average measure of 7 days' actual table salt use, the average sodium contribution of 17 high-sodium foods from a food frequency checklist maintained for 7 days, a calculation of drinking water sodium, and measurements of height and weight to establish 24-hour energy needs, a surrogate estimate of sodium found in all foods not included in the food frequency checklist. Participants were studied for 16 days: 7 consecutive days on either a 2,000-mg or a 3,500-mg sodium diet, 2 days' adjustment, and 7 days' crossover. Participants were allowed to select foods from a diverse menu, eat at fast-food restaurants, and consume alcohol if desired. Mean of 7-day sodium intake obtained with the instrument was significantly correlated with mean of 7-day sodium intake determined by food analysis (r = .80), from food composition tables (r = .62), and from urinary excretion (r = .56).