Using photon absorptiometry the forearm bone mineral content (BMC) was determined in 75 children aged 4 to 16, who all had a low birth weight. Forty-five of them were born preterm AGA (27 boys, 18 girls, mean weight 1 580 g; range 920-2 060 g) and 30 preterm SGA (17 boys, 13 girls, mean weight 1510; range 940-2130 g). The results were compared with a control group of children of the same age, and analyses of covariance with age, height and weight as the covariant factors were performed. The BMC, weight and height did not differ between the children born AGA or SGA. Irrespective of AGA or SGA, the BMC was significantly decreased in boys but the difference was less pronounced and less significant when height and weight were used as covariant factors. Boys who had been born preterm had a less BMC than the control boys for their age but they were also somewhat shorter and lighter than expected with regard to their age.