Prevalence, type, and magnitude of scoliosis were studied in 163 patients with myelomeningocele. A scoliosis was diagnosed in 143 of them, congenital in 15 percent of the cases and developmental in the remaining patients. The severity of scoliosis increased with age and was more severe the higher the level of the neurologic deficit. The direction of the curves was correlated with pelvic obliquity, but not with hip dislocation. Although some patients with low level anomalies may develop severe scoliosis, patients with levels above L3 run a considerably higher risk in this respect. The radiographic baseline examination of the spine carried out in the newborn seems to permit a reasonable prognosis in regard to future scoliosis. Gross syringohydromyelia caused or contributed to scoliosis in 5 percent of the cases. However, less extensive syringohydromyelia and Chiari malformations due to abnormal neuromuscular control also promote the development of scoliosis in these patients.