In the spring of 1992 schoolchildren (679 boys and 661 girls) aged 6-12 years in a school in central Hanoi, Vietnam were enrolled for a medical examination including measurements of height and weight. Most of them were measured a second time almost exactly 1 year after the first measurement. Thus, values for height, weight, and body mass index (BMI), and their yearly increments were obtained for the ages 7-11 years. When these heights and weights were compared with those for children from Bangkok, Tokyo and Sweden, the Hanoi values were very close to the Bangkok ones. There were overall no significant differences in height, weight, and BMI between children whose parents were of different occupational and educational groups, except for girls whose mothers were workers/farmers, who were shorter (P <0.05), lighter (P <0.01), and had a lower BMI (P <0.05) than girls whose mothers were from upper occupational status (government staff). The overall incidence of low birthweight (<2500 g) was 11 per cent, but this was not associated with either parents' occupation or education. At the time of measurements 31.6% of the children were rated by the doctors as being in 'general bad condition'; there was a higher proportion of girls than boys (P <0.01) and a higher proportion of girls whose mothers were workers/farmers (P <0.001).