The purpose of this study was to explore the potential of applying arthroscopic techniques to autogenous bone grafting of long bone fracture delayed union. There were 9 patients in this initial series, including 4 patients (average age, 37 years) with humeral lesions and 5 patients (average age, 25 years) with tibial fractures. There were 6 men and 3 women. Techniques customarily employed in arthroscopy were used to visualize, expose, and deliver the onlay cancellous bone grafts. Bony union occurred in all but 1 patient in an average of 4 months. This patient had a fibrous union and sustained a reinjury that led to successful repeat open bone graft surgery. The arthroscopic approach for bone grafting of certain long bone delayed union appears to be a safe and effective procedure. The procedure is best suited for patients with mechanically stabilized fragments, and it lends itself to those with overlying skin or soft tissue compromise. There are some relative contraindications: grossly unstable fragments, severe malunion, and/or infection.