Diabetes mellitus type 1 might interfere with pubertal development. Particularly, long-term metabolic control and intensity of insulin treatment have been reported to contribute to a delay in pubertal onset. Data on somatic development in diabetic children are conflicting; therefore we studied bone age in 1788 children from Germany and Austria with type 1 diabetes. Bone age was retarded by -0.27 +/- 1.1 years in the whole group, but particularly in the adolescents at the end of puberty (>16 years; -0.76 +/- 1.29y). Bone age delay was more pronounced in boys, and in children with long-term median HbAlc levels of 7.5 - 9.0%. No associations were found with current HbAlc levels or the intensity of insulin treatment. Bone age determinations in diabetic children should only be performed when clinical signs of impaired somatic development are present. In addition, the potential influence of diabetes on bone development needs to be considered in the interpretation of carpograms.