Objectives. Surgical treatment is standard for advanced osteochondritis dissecans (OCD) of the humeral capitellum. When cartilage is seen to be separated or completely detached, this fragment fixation is not usually applied. There have been reports of cases in which advanced OCD of the humeral capitellum progressed to osteoarthritis (Fig), particularly in cases which involved the lateral wall. In these cases, every attempt should be made to reconstruct the lateral wall to avoid osteoarthritis. In this study, we followed up cases with rib osteochondral autograft transplantation technique. Methods. Subjects were 20 cases who were followed up until after they started pitching. The mean age was 13.8 years old and the mean observation period was 2 years and 6 months (from 7 months to 6 year 3 months). Kocher's approach was used to give a good access to the aspect of the radiohumeral joint. The majority of cases suffered from extensive OCD of the elbow. Detached fragment was removed (Fig. 2a) and graft from 5. th. or 6. th. rib with screw fixation was performed on 12 patients and 8 received fixation with no material (Fig. 2b). Follow-up assessment included the range of motion, start time of playing catch and throwing a ball with full power, sports activity, evaluation of radiography, a subjective (including Pain, Swelling, Locking/Catching and Sport activity) and objective (Flexion contracture, Pronation/Supination and sagittal arc of motion) modified elbow rating system by Timmeman et al. We also investigated the details of the arthroscopy observations and the 2nd arthroscopy findings for 4 cases. Results. Preoperative elbow extension increased from −13.5 to −10 degrees and elbow flexion increased from 117 to 123 degrees, but no significant differences were found. All but one patient resumed baseball sporting activity. Catching was started at an average of 3.5 (2 to 5.5 months) months postoperatively and pitching the ball with full power was achieved at 6.7 months. One case was found to have degenerative changes on plain X-ray, and two cases were found to have deviated screws. The mean elbow rating system subjective score improved significantly from 63.9.5 to 89.5 points, as did the overall rating, increasing from 131.6 to 164.8 points. The 2. nd. arthroscopy observations for 4 patients showed that 2 experienced pain due to the loose body, 1 had a limitation in range of motion due to spur formation, and 1 had a screw deviation. Graft survival was observed in two out of four cases. Partial detachment was observed in two cases. Conclusion. Recovery of articular facets with hyaline cartilage were possible using this surgical technique, and in addition, the costal-costochondral grafts, comprising cortical and cancellous bone, were simultaneously transplanted en bloc. This indicates that it is adequate treatment for extensive OCD. All the patients started pitching 3 months postoperatively and returned to full baseball activities after 6 months. Even in cases with extensive OCD, with large osseous and cartilaginous deficits, the surgical technique was useful and showed favorable results