We report our findings of a prospective outcome study of a series of 50 patients with chronic ACL injury undergoing arthroscopically assisted bone-patellar-tendon-bone ACL reconstruction. Patients underwent reconstruction if they had instability precluding participation in sport at the desired level and were reviewed at a mean of 62 months. Clinical examination was carried out pre and post operatively. Assessment was augmented by KT 1000 measurement, Tegner activity score and Lysholm score. Surgery was considered a failure if the Pivot Shift test was 2+(jerk) or symptoms of instability persisted. By these criteria 48 patients were successfully treated. Our results show a good medium term outcome for this reconstructive method. We had a 94% return to sporting activity but at a lower than expected activity level. Clinical examination showed an improvement and we recorded excellent or good results on Lysholm score in all these patients.