Lumbar spine (L-2, L-3, L-4) bone mineral density was measured in 184 healthy boys and girls aged 5.00 through 11.99 years by dual photon absorptiometry. Weight, height, age, triceps skinfold thickness, and midarm circumference were also measured. Weight, height, and age were highly correlated with bone mineral density. In the population studied, a quadratic regression equation using body weight as the independent variable best described bone mineral density: bone mineral density = 0.3209 + [0.0168 (weight)] - [0.0001 (weight2)].