The change of the difference in height between two socially extreme groups of 10 year old Stockholm children born in 1933, 1943, 1953 and 1963 was analysed. Data on height and social conditions were taken from the school health records. The two groups were established on the basis of the father's occupation and the number of children in the family. The height of the 10 year old children in the more privileged group born in 1933, 1943 and 1953 was virtually unchanged, but the height in the less privileged group increased gradually. The difference between the two groups was levelled out in the 1953 cohort. However, it reappeared in the 1963 cohort, mainly as a result of increasing height in the more privileged group and fairly unchanged height in the less privileged group.