Unicondylar osteoarticular allografts (UOA) of the knee are mainly used after bone tumour resections for benign aggressive tumours or small malignant tumours with clearly defined margins. They are also used less often in large posttraumatic condylar defects. Between 1989 and 2004, 12 deep-frozen UOA reconstructions (in 11 patients) were performed at our Institute. The diagnosis was chondrosarcoma in four cases, giant cell tumour in three, osteosarcoma in three, posttraumatic defect in one, and one failed UOA. The involved site was the medial femoral condyle in six cases, the lateral femoral condyle in three, the medial side of the tibial plateau in two, and the lateral in one case. One allograft was removed after 29 months because of an intra-articular displaced fracture, and substituted with a new UOA. One patient died of metastatic disease at 24 months. We report the functional and radiographical outcome of the remaining 10 UOAs with a minimum follow-up of 4 years (average 11 years). Two of the 10 patients had excellent results, five were good and three were fair. Radiographically, five patients had "mild" and five had "severe" degenerative changes. One patient with severe degenerative changes had pain and stiffness, therefore the UOA was converted into a prosthesis allograft composite, using a conventional total knee prosthesis. In selected cases of distal femoral and proximal tibial tumours, UOA reconstructions give good functional outcomes with relatively few major complications.