As to treatment of meniscal tear, meniscal repair is shown to be an attractive therapy in comparison with meniscectomy if considering meniscus function in human being such as loadbearing and a second restraint etc.. It is difficult to investigate the postero-medial corner knee joint by arthroscopy, but it is easy to find meniscal tear in it by arthrography. For 4 cases with longitudinal tear of middle and posterior segments of medial meniscus combined with ACL injuries, we performed positive single contrast arthrography before and after meniscal repair. We could find meniscal tear accurately in all cases arthrographically. On the other hand we could suspect meniscal tear in only 2 cases arthroscopically. After repair we found arthrography to be useful for determining repaired meniscus to be healed.