Sixty-three first, second, or third-time repairs of one or more pseudarthroses were done in fifty-one patients who had had an arthrodesis for idiopathic scoliosis. Forty-five of the patients were female and six were male. The average age was 30.2 years. The indications for the sixty-three repairs were pain (twenty-five repairs), progression of the curve (sixteen), both pain and progression of the curve (twelve), and radiographic changes only (ten). Failure of the implant was identified before 27 per cent of the sixty-three procedures. The pseudarthroses were diagnosed an average of 2.8 years after the initial arthrodeses. Sixty-eight per cent of the defects were visible on plain radiographs preoperatively and 32 per cent were identified at operation. During the time between the original arthrodeses and the repairs of the pseudarthroses, the scolioses increased by a mean of 7 degrees and the kyphoses, by a mean of 10 degrees. Harrington distraction was the most commonly used instrumentation (twenty-six [41 per cent] of the sixty-three procedures), and autogenous iliac bone was the most commonly used material for the graft (thirty-three [52 per cent] of the procedures).