An arthroscopic examination of 59 canine stifle joints, both normal and diseased, was carried out. Endoscopically the stifle joint was divided into five main anatomical compartments - the suprapatellar pouch, femoropatellar joint, medical compartment, intercondylar notch and the lateral compartment. It was possible to identify all the intra-articular structures using a single infrapatellar approach and the technique allowed an assessment of the non-osseous structures of the joint. Pathological changes were appreciated. eg, hypertrophy of the synovial membrane, articular cartilage fibrillation and erosion, meniscal degeneration and osteophyte development. The arthroscopy and biopsy forceps allowed synovial membrane biopsies to be taken under direct vision. Arthroscopy is likely to become a useful aid to the diagnosis and assessment of joint disease in the veterinary patient but it is a technique which requires patience and practice before it can be used proficiently.