To determine the influence of hemoglobinopathy on growth and development, we examined the height, weight, and sexual maturation of 2115 patients 2 to 25 years old who had homozygous sickle-cell disease (SS), SC disease (SC), sickle beta+ thalassemia (S beta+), or sickle beta O thalassemia (S beta O). Using regression analysis of these cross-sectional data to generate growth and maturation curves for each hemoglobinopathy, we found that the curves for all hemoglobinopathy groups were significantly different from published norms for black subjects (P less than 0.001), and that subjects with SS and S beta O were consistently smaller and less sexually developed than those with SC and S beta+ (P less than 0.001). For both sexes and all hemoglobinopathies, low weight was more pronounced than short height and was most apparent in subjects over the age of seven. The median age of the female subjects who had attained at least Tanner Stage V was 17.3 years for those with SS, 17.2 years for S beta O, 16.0 years for SC, and 16.5 years for S beta+; among male subjects the corresponding values were 17.6, 18.8, 16.6, and 16.6 years. Discriminant analysis of menarche status, weight, age, and hemoglobinopathy revealed that the influences of age and weight on menarche were similar regardless of hemoglobinopathy. This relationship suggests a constitutional rather than a primary endocrinologic cause of sexual immaturity in patients with hemoglobinopathies.