We reviewed the results, after follow-up ranging from twenty-three months to six years, in thirty-four patients who were treated during childhood for hematogenous osteomyelitis of a major long bone complicated by sequestration of a portion of the diaphysis and by pseudarthrosis or segmental bone loss, or both. Of the thirty-four lesions, twenty-four were in the tibia, eight were in the femur, and two were in the humerus. In twenty-three patients (Group I), the infection was still active, while in the other eleven (Group II), it was quiescent at the time of admission to the hospital. In nine of the patients in Group I (four tibial and five femoral lesions), an involucrum bridged the osseous defect, indicating that the periosteal tube had not been destroyed. In these nine patients, sequestrectomy and debridement, appropriate antibiotic therapy, and prolonged immobilization in a plaster cast resulted in healing of the defect without recurrence of the infection. In the remaining fourteen patients (twelve tibial and two femoral lesions), there was no periosteal new-bone formation, and operative treatment consisted of two stages: the first, to resolve the infection, and the second, to heal the osseous defect with corticocancellous iliac grafts. In the eleven patients in Group II (eight tibial, one femoral, and two humeral lesions), there were no involucra. All of these patients were treated with cancellous bone grafts and prolonged immobilization. In twenty-two of the thirty-four patients (thirteen in Group I and nine in Group II), there were varying degrees of angular deformity at the pseudarthrosis, necessitating correction by manipulation when the plaster cast was applied postoperatively (ten patients), by fibular transposition (six patients), or by fibular osteotomy in addition to manipulation (six patients). Excluding complications specific to the fibular transfer procedure, the complications in the Group-I patients (six recurrent postoperative infections, one fracture of the graft, and one non-union of a fibular strut graft) were approximately as frequent as those in the Group-II patients (one failure of fusion and two fractures of the graft). Operative treatment resulted in healing of all but one tibial lesion, in a patient who nonetheless had good function at follow-up. Of the seven limb-length discrepancies of 2.8 centimeters or more, by the latest follow-up two had been treated uneventfully: one by femoral and the other by tibial lengthening.(ABSTRACT TRUNCATED AT 400 WORDS)