Radiographic increase in the size of tibial and femoral tunnels has been observed following the reconstruction of the ACL with a bone-patellar tendon-bone autograft. The purpose of this study is to determine if any differences exist in the amount of enlargement of the bone tunnel with the clinical results and to know the factors which affected to the enlargement of the bone tunnels. Total 27 patients were retrospectively reviewed for tunnel enlargement radiographically at one year after operation. Anteroposterior and lateral x-ray were obtained and the tunnel were measured by two independent observers. The measurements were made at the widest part of the tunnel. The distance between tibial interference screw and knee joint line also measured. Correction for magnification was performed by comparing the measured width of the interference screw used for fixation of the graft with its actual width. Statistical analysis was performed with Wilcoxon rank sum test. The radiographic tunnel enlargement was an average of 1.7±1.3mm for the femur and 1.9±0.8mm for the tibia. The proximal migration of the tibial interference screw was an average of 2.3+±1.1 mm. There was no statistically significant correlation between the changes in tunnel diameter and either the modified Hughston knee score, Lysholm knee score, or the joint laxity measured by a KT-2000 arthrometer, Lachman test. There were no correlations between the mild proximal migration of the tibial interference screw and the clinical results. Conclusively, the tunnel enlargement and mild proximal migration of the interference screw did not appear to affect the functional outcome adversely. It needs longer follow up for the evaluation of etiology and natural history of this tunnel enlargement.