To localize optimal donor regions for osteochondral graft transplantation, the chondral thickness and the radii of curvature of femoral condyles and the talar trochlea were determined. Optosil impressions of the articular surfaces of ten formalin fixed distal femora and talar domes were prepared. Therefrom, 5-mm thick frontal sections were made in order to measure the radii of curvature. Femoral condyles and talar trochleas were sliced sagittally into 2-mm thick sections. Chondral thickness was measured on x-rays. Talar cartilage thickness measured 0.7 to 2.0 mm. Cartilage thickness of the femoral condyles was 0.7 mm to 3.1 mm. The smallest radial values of the talar surface were proximal and distal. Flattening of the medial and lateral talar margins and of the central articular surface was evident. For the femur, the curvature was greater in the edge areas than in the central region. For talar defects, the grafts should be taken from the condylar edges, where the chondral thickness is decreased.