To evaluate the efficacy of arthroscopic reconstruction of the anterior cruciate ligament (ACL) injury with "bone-patellar tendon-bone" (BPTB), fixed with interference screw of outside in technique, we compared the results of this technique with those of open technique. Fifty cases of isolated ACL tear was treated with reconstruction of the ligament. Twenty eight knees of open reconstruction and twenty-two knees of arthroscopic reconstruction were involved in this study. The follow-up period was 48 months (24-72 months) in average for the open procedures and 20 months in average (16-24 months) for the arthroscopic procedures. The laxity was measured in Lachman test position with OSI Sagittal Knee Tester. The results were graded as grade (0-1.0 mm), grade Ia (1.1-3.0 mm), Ib (3.1-5.0 mm), II (5.1-10.0 mm) and III (more than 10.1 mm). The results were as follows; 1) Twenty four out of 28 knees (85.7 %) of open reconstruction group and 19 (86.4 %) out of 22 knees of arthroscopic reconstruction group showed grade 0. 2) Only one case (3.6 %) showed grade Ia and another 3 cases (10.7 %) showed grade II in the open reconstruction group. Two cases (9.1 %) showed grade Ia and another 1 case (4.5 %) showed grade Ib in the arthroscopic reconstruction group. There was no statistically significant difference between the two groups (P > 0.05). 3) All fifty cases showed muscle atrophy of the thigh. In 12 weeks after operation, 25 knees (89.3 %)of open reconstruction group and 18 knees(81.8 %) of arthroscopic reconstruction group showed 2 4cm thigh girth difference compared with normal side, which showed no statistical difference between the two groups (P>0.05). 4) In 12 weeks after operation, only 5 knees (17.9 %) of open reconstruction group showed normal range of extension, whereas 17 cases(77.3 %) of arthroscopic reconstruction group showed normal extension, which was significantly different (P<0.05). However no case of either group showed more than 5 degrees of flexion contracture at final follow-up. In conclusion the results of arthroscopic reconstruction of the ACL with 'bone-patellar tendon-bone' was at least comparable to open reconstruction.