Of 400 patients with the diagnosis of neurofibromatosis on their hospital records, 141 actually had the disease. The presence of at least two of the following features was considered diagnostic: positive family history; positive biopsy; a minimum of six cafe-au-lait spots, each with a diameter of at least 1.5 centimeters; and multiple subcutaneous neurofibromas. Scoliosis was present in thirty-seven patients (26 per cent), most commonly associated with cafe-au-lait spots (thirty-five patients). In many of the patients with scoliosis there were associated medical and surgical problems. Although no standard pattern of spinal deformity could be identified, a sharp single right thoracic curve involving more than five vertebrae was the most common. For the whole group the initial measurement of the scoliosis averaged 42 degrees. Double curves were more sever, buth kyphosis was uncommon and no cases of paraplegia were recorded. In patients with progressive scoliosis, the best results were obtained with early Harrington instrumentation and posterior spine fusion. Progression of the scoliosis was observed both before treatment and postoperatively. The amount of progression was not necessarily related to the severity of other manifestations of neurofibromatosis, and was not significantly dependent on the length of the curve.