Data from the 1972, 1982 and 1990 surveys of the National Study of Health and Growth were used to calculate changes in height, weight, triceps skinfold thickness and weight-for-height index for children aged between 4.5 and 11.99 years. There were data for 7887, 6396 and 6420 white English children in the 3 years respectively, and data for 1586, 1191 and 1317 Scottish children. Increases in all measurements were found from 1972 to 1990, except for weight-for-height in English boys, and were generally greater from 1982 to 1990 than from 1972 to 1982. Approximately a third of the increases in weight-for-height and triceps skinfold thickness from 1972 to 1990 were associated with increases in parental body mass indices and decreases in family size. No consistent differences in trends were found between social groups. Greater trends were found for girls and for Scottish children, and Scottish boys are now heavier and fatter than their English counterparts. Trends in weight-for-height and fatness may have implications for future trends in coronary heart disease, and lessen the likelihood that the targets for reductions in obesity in the White Paper Health of the Nation will be met. Preventive measures should be directed at the entire population.