The effect of early (mean, 5 months) versus late (mean, 9 months) return to vigorous cutting activity on the long-term outcome of anterior cruciate ligament reconstruction was evaluated retrospectively. Sixty-four reconstructions, using a distally attached medial one-third patellar tendon, were reviewed on an average of 46 months postoperatively. After surgery, the timing of return to vigorous activity was based on biologic fixation of the graft, a negative Lachman test, absence of effusion, and the patient's desire to return to previous activity. The 64 patients were retrospectively separated into two groups. The early group consisted of 31 patients who returned to activity 2 to 6 months after reconstruction, and the late group consisted of 33 patients who returned to activity 7 to 14 months after reconstruction. By clinical examination, KT-1000 arthrometer measurements, subjective evaluation, and Cybex testing, there were no differences between the early and late return groups except for reestablishment of final range of motion. At an average followup of 46 months, this study indicates that an early return to vigorous physical cutting activities after ACL reconstruction does not predispose patients to reinjury or a less satisfactory longterm result.