Measurements of height, weight and triceps skinfold thickness were obtained from English and Scottish schoolchildren from 15 birth cohorts over the period 1972-1980. Positive trends in weight were found for boys and girls in both countries, but in England they were less than expected from the increases in height. The increase in weight-for-height in Scotland was paralleled by a greater increase in triceps skinfold in Scottish than in English children. Scottish children remained shorter, lighter and thinner than English children, but similar in weight-for-height. Separate monitoring of trends in obesity for English and Scottish children should continue.