Over 400 cruciate ligaments were reconstructed with the newly developed scaffold type Leeds-Keio artificial ligament made of polyester. In this survey, 146 ACL cases with over 36 months postoperative history were clinically and in some cases arthroscopically and histologically reviewed. In the first series of 80 cases, ACL was reconstructed intra-articularly alone, and in the second series of 66, extra-articular lateral stabilization was added to the intra-articular procedure. In the first series, the Lachman test was improved in 88%, anterior drawer sign in 80% and jerk test in 75%. In the second, these were improved to a much greater degree, so that the corresponding figures were 95%, 86% and in 91% respectively. There were no complications such as joint effusion, chronic synovitis and infection. Revision due to implant rupture was done in 8 cases. Postoperative arthroscopy showed coverage of the implant by new tissue and development into a biologically sound ligament by 12 months postoperatively. Histological examination of the biopsy specimen obtained in arthroscopy showed abundant collagenous fibres running longitudinally. These results indicate that the Leeds-Keio artificial ligament yields satisfactory clinical results.