A severe bone abnormality was observed in a 3 year old white female which led to a family study of 4 generations. Nine of the 14 members of the family revealed some degree of involvement. The most severe changes were found in the original case (Case 1) and the mother (Case 5). The youngest patient was 16 months of age.A second family, representing 3 generations, presented 3 similar cases (Cases 10, 11 and 12) and possibly a fourth case (Case 13). The youngest patient was observed in utero.A total of 18 members of the 2 families was studied. Thirteen of these, 9 females and 4 males, showed some degree of bone involvement. The roentgenographic and clinical findings were practically identical in both families.The disorder is presented as a possible new entity among bone dysplasias.