A series of 104 patients with paraplegia has been reviewed. All were patients at the Massachusetts Hospital School between 1948 and 1963 and all had paraplegia during childhood or adolescence. The characteristics and development of their deformities were analyzed. Ninety-seven were found to have deformities of the spine and pelvis. Lordosis was by far the most common, but thirty-six had scoliosis and fourteen kyphosis. Many had mixed deformities with combinations of lordosis and scoliosis or kyphosis and scoliosis. In each group the patients were classified balanced, partially balanced, or off balance. An attempt was made to ascertain the reasons for the particular deformities. Lordosis was attributed to the combined effects of paralysis and position of the trunk in the upright position. In the tripod stance, characteristic of paraplegics, balance and stability are maintained by inclining the body forward. The result is an anterior curve of the vertebral column which extends throughout the area of paralysis. Scoliosis was added to the lordosis when the vertebral column was curved laterally for any reason such as a hemivertebra, incomplete lateral segmentation, or scoliosis of unknown cause. Scoliosis was also often initiated and aggravated by a chronically assumed position. Kyphosis could be attributed to anomalous vertebral development or to traumatic deformity in all cases. All deformities tended to become worse during growth, unless arrested surgically. They all increased in severity and most of them lost correctability, especially scoliosis and kyphosis. The pelvis followed the spine forward into lordosis or backward into kyphosis. In the presence of lumbar scoliosis the pelvis was displaced into obliquity and rotation in accordance with the curvature and the rotation of the spine. In some patients, the scoliosis could be attributed to muscle imbalance about the hips and pelvis. Dislocation of the hip which often accompanied pelvic obliquity, together with paralysis of the gluteus maximus muscles, tended to increase the lordosis. Harrington instrumentation and spine fusion including the sacrum was found to be the most effective means of controlling spine and pelvic deformity associated with childhood and adolescent paraplegia. The procedure has been used in too few patients and for too short a period of time for definite conclusions. Its use will be continued.