Eighty-seven families with early onset scoliosis were evaluated. These were divided into 3 groups: resolving infantile idiopathic scoliosis (15 families), progressive infantile idiopathic scoliosis (21 families), and congenital scoliosis due to vertebral malformations (51 families). The children with congenital scoliosis were subdivided into those who had closed neural arch defects (19 families) and those who did not (32 families). Resolving infantile idiopathic scoliosis was usually associated with plagiocephaly, and both deformations tended to show spontaneous recovery. These children were otherwise normal. Seven (33%) of the children with progressive infantile idiopathic scoliosis were mentally retarded, but only 2 had a congenital malformation. In contrast, 18 (33%) of the children with congenital scoliosis had other malformations, but only 2 were mentally retarded. The recurrence risk for scoliosis was low in each group studied. However, there was an increased risk (4% for sibs) of neural tube defects in the families with congenital scoliosis (with or without neural arch defects). This sib risk was apparent for probands with only a single hemivertebrum in addition to probands with more extensive vertebral defects and would support an etiological relationship between neural tube defects and other vertebral malformations.