We studied the relationship between dietary salt intake, urinary salt excretion, blood pressure and anthropometric measurements in 322 Japanese schoolchildren, aged between 6 and 11 years. Two surveys were carried out: one among a small group of 22 children from the 322, and one involving all 322. In the former group, both a detailed and a simplified dietary questionnaire were used, and nocturnal and 24 hr urinary salt excretion samples were collected. The latter group's survey used only the simplified questionnaire and nocturnal salt excretion measurements. The surveys from the two different groups were then compared to each other. It was found that the simplified questionnaire and nocturnal urinary samples were statistically accurate enough to be used for the purpose of this study. From the latter survey, dietary salt intake among the children was 7.5 +/- 2.7 g per day, (mean +/- SD), and 65 pupils (20%) consumed more than 10 g of salt per day. It was also found that nocturnal urinary salt excretion levels were 1.47 +/- 0.82 g per day, with 30 pupils (9.3%) registering levels of more than 2.5 g per day. There was a significant correlation between these dietary and urinary salt levels. Systolic blood pressure (SPB) among the schoolchildren showed significant correlation with age, height, weight and BMI. For diastolic blood pressure (DBP), a significant correlation was seen in age only. SBP and DBP showed little relation with either dietary salt intake or urinary salt excretion.(ABSTRACT TRUNCATED AT 250 WORDS)