The types of the synovial plicae were classified according to the classification of Kim and Choe(1997). The purpose of this study was to evaluate the diagnostic ability of MRI for synovial plicae. We retrospectively reviewed the MR findings of the knee in 95 cases of 91 patients. In all 95 cases, findings of arthroscopy and MR images were available. MRI was performed with a 1.5 Tesla Magnetom(Siemens) using a round surface coil. Pulse sequence were Tl weighted image(TR 650ms /TE 20ms) and T2 weighted image(TR 2000ms/TE 70ms). MR images could not show the infrapatella plicae and lateral plicae clearly, but some suprapatellar plicae were shown in T2 weighted MR images (37.5% of hole type, 80% of complete type, 26% of medial type). In 20(22%) of the 90 cases with medial patella plicae proved by arthroscopy, a low intensity band was shown above the medial condyle of the femur on T2 weighted MR images. These 20 cases included 3 of fenestra type, 9 of wide shelf type and 8 of medial shelf type. The low intensity band seen on T2-weighted MR images and its anatomical relation to the medial femoral condyle are helpful in diagnosing the presence of medial shelf type and wide shelf type of medial plicae.