Fifteen cases of ununited diaphyseal fractures of femurs were treated successfully by intramedullary reaming and closed Küntscher nailing through the small gluteal incision. The equipment used is the same as for nailing fresh shaft fractures. The cases included 10 nonunions, 2 delayed unions and 3 miscellaneous problems. All but one case had been initially treated by open reduction with some form of internal skeletal fixation. Two cases had been treated by 2 open procedures befor the closed Küntscher nailing. No supplemental bone graft or external immobilization was necessary. Two cases were nailed successfully in the presence of infection, resulting in solid union and no recurrence of infection. Five nails have been removed after union and no refracture has occurred. No important postoperative complication or instances of the fat embolism syndrome were encountered. No rotational deformity or further shortening of the femur occurred. Postoperatively, the patients ambulated with protected weight-bearing as early as possible. The average hospital stay was 15 days. In general, the patients had a functional extremity even while the fracture lines were still visible on roentgenographs; all have returned to their previous work.