The mesomelic dysplasias are a heterogeneous group of genetic disorders with predominant skeletal manifestations in the forearms and shanks. We have documented, over a thirteen-year period, the clinical and radiographic course of the condition in a boy with the Langer type of mesomelic dysplasia. It has been suggested that dyschondrosteosis or the Madelung deformity are the phenotypic manifestations of the gene which causes Langer mesomelic dysplasia in the homozygote. Several relatives on both sides of the family which we studied had malformations of their forearms, in keeping with this concept. However, these anomalies differed from those of dyschondrosteosis and the classical Madelung deformity; the exact syndromic status of the heterozygous phenotype remains unsettled.