Body shape, defined by detailed anthropometric measurement, was compared in 64 children with homozygous sickle cell (SS) disease, and in 123 children with a normal Hb (AA) genotype, aged 4-6 yr. Children with homozygous sickle cell disease showed an average reduction in weight, height, sitting height, limb length, interacromial and intercristal diameters and skinfold thickness. They showed increased anteroposterior chest diameters with an increased anteroposterior-lateral chest diameter ratio. The effect of homozygous sickle cell disease on growth patterns in childhood is apparent before the age of 6 yr. The relationship to changes in body shape, seen during adolescence and in affected adults, and their possible determinants, are discussed.