When diagnosing disease of the stifle in dogs ultrasonography is a good addition to clinical and radiological examination. Radiology can evaluate the bony aspects of the joint and their relationship to each other. In contrast, sonography allows visualization of the soft tissue. For most evaluations the 7.5 MHz linear scanner is suited best. Normal stifles of 58 dogs of different breeds were evaluated using a standardized examination procedure. This procedure had been derived from that used in humans. The stifle is divided into several regions which are examined and evaluated. These are the suprapatellar, infrapatellar, lateral, caudal and medial region. One hundred twenty seven patients which had problems associated with the stifle joint were examined sonographically after a clinical and radiographic exam. Osteochondrosis dissecans, ruptured cranial cruciate ligament, meniscal damage, arthritis, tumor, post surgical conditions, injuries of the patella, patellar ligament or tibial tuberosity and luxating patella were examined sonographically and the findings recorded.