We reviewed the cases of eight unrelated children who had an unusual form of enchondromatosis characterized by unilateral enchondromas arising within the epiphyseal and metaphyseal regions of the long tubular bones of the lower extremity. Unlike previously described enchondromas, the lesions developed extensively within the epiphysis before closure of the growth plate and there was direct extension across the epiphyseal growth plate into the metaphysis. The lesions resulted in severe limb-length discrepancy and angular deformity (which increased in every patient after the time of presentation), asymmetrical premature physeal arrest, and joint incongruity, all of which necessitated numerous operative procedures. Seven patients had limb-lengthening and one had a Boyd amputation without lengthening. Five patients had a second lengthening procedure. Twenty-seven osteotomies (range, one to five procedures per patient) were done; six patients had a repeat osteotomy. Four patients had an epiphyseodesis. We believe that these lesions represent a previously undescribed clinical entity, which we termed epiphyseal-metaphyseal enchondromatosis.