1. A group of children with congenital malformations of the lower back involving the spinal cord or nerve roots is described. The malformations have little or no resemblance to spinal rachischisis, either embryologically or clinically. The lesions found are often complex. 2. It is considered from clinical and operative findings that the malformations are, in many patients, responsible for increasing neural damage in childhood and even in later life. 3. Early investigation and operative treatment are recommended.