diagnosis of knee joint pathology has been mainly dependent on clinical manifestations and invasive procedures such as arthrography and arthroscopy etc. However, these procedures are invasive, Arthroscopy is performed under general anesthesia. Recently, with development of high resolution CT with thin slices and multiplanar reconstructions capability, CT could be used to verify the internal structures of knee joint in noninvasive or less invasive way. From June to December 1985, authors have experienced 19 cases of the knee joint CT. Among them, 13 cases were operated and confirmed. We concluded as follows. 1. The diagnostic accuracy of the knee CT was 100% in lateral meniscal tearing 92.3% in medial collateral ligament, 100% in tearing of cruciate ligaments. 2. CT could be considered as a primary diagnostic procedure in the knee pathology rather than more invasive arthrocopy or arthrogrphy. 3. for the accurate diagnosis of knee joint pathology, CT, which can obtain thin slies high resolution, multiplanar reconstructions, is indispensagble.