[en] To evaluate the efficacy of MRI in assessing anterior cruciate ligament (ACL) reconstruction graft integrity, we compared MRI findings with arthroscopic findings in 52 patients who had undergone arthroscopically assisted ACL reconstruction using semitendinosus and gracilis tendons augmented by woven polyester. MRI and arthroscopy were carried out 12 months after the operation. The MR appearance of ACL grafts was categorized into 3 types by signal intensity and continuity of the ligament according to Rak's method: well-defined type: the graft was visualized as a smoothly continuous band with low signal over the entire course; intermediate type: signal intensity increased and a low-signal band was visualized only in part of the graft; indiscernible type: the graft was not identified through the joint cavity due to markedly increased signal intensity. When the MR appearance of intermediate or indiscernible types was defined as torn, the grafts were presumed to be torn in 9 patients whose arthroscopic findings were 7 intact and 2 torn grafts. All cases with intact MRI findings were intact on arthroscopic examination. Thus, the sensitivity, specificity and accuracy of MRI as an evaluative tool for ACL graft tears were 100%, 86% and 86.5%, respectively. (author)