A variety of substitutes and numerous operative procedures have been described to stabilize the anterior cruciate ligament(ACL) deficient knee. OBJECTIVES: The purpose of this study has been to evaluated the remodelling process of bone-patef- lar tendon-bone(B-PTB) allograft(Tutoplast(r)) for ACL reconstruction by means of light microscopic(LM) and electron microscopic(EM) examinations from the biopsy specimens obtained at the time of second-look arthroscopy. The authors also have been grossly observed the width, vascularity, elasticity and stability of B-PTB allograft. MATERIALS AND METHODS: ACL reconstruction using B-PTB allograft was performed on 22 consecutive patients. Among them, 12 patients were reviewed and the average age at time of operation was 22.5 years ranging from 21 to 40 years. The second look arthroscopy was performed at 6 months, 12 months, 24 months in each of the 4 cases. The gross findings of allograft were observed, and biopsy was done by the method of Millonig. Results; The arthroscopic findings of the reconstructed ACL were partially covered with synovium and narrowed in diameter at 6 months follow up. At 12 months follow up after reconstruction, that grafted ligaments were covered with more synovial membrane, and observed the more thickness with normal strength similar to normal anterior cruciate ligament configuration. At 24 months, grafted ligaments were grossly similar to normal ACL. The LM findings demonstrated many fibroblasts with spindle shape nuclei and and hypercellularity at 6 months. At the 12 months, crimp pattern of collagen bundles and decreased hypercellularity observed. At 24 months, grafted ligament were similar to nomal ACL. The EM findings that fibroblasts were showed abundant cytoplasm which contained marked dilated rough endoplasmic reticulum(r-ER) and aggregates of microfilaments at 6 months. At 12 months, fibroblasts with folded nuclei and abundant cytoplasm were observed. At 24 months, demonstrated the fibroblasts with abundant cytoplasm and densely packed collagen fibrils. Collagen fibrils displayed parallel arrangement and characteristic cross striation with a periodicity. Scanning EM findings showed uniformly small diameter of collagen in the transeverse section. CONCLUSIONS: Gross & LM findings of B-PTB allograft were similar to that of normal ACL at 6 months, and at 12 months, postoperatively. But EM findings of B-PTB allograft were compared with the biopsy samples of normal ACLs, the allograft was still undergoing maturation 24 months postoperati vely.