Reconstruction of the anterior cruciate ligament using a hamstring tendon autograft has often been recommended for female athletes. We compared the results of acute, isolated, intraarticular anterior cruciate ligament reconstructions using quadruple-looped hamstring autografts in 39 female and 26 male patients. All reconstructions were performed by the same surgeon using a similar surgical technique and the same postoperative management. In each case, patients had Endobutton femoral fixation and either post or button fixation for the tibial side. The average follow-up was 40.9 months for women and 39.0 months for men. Objective analysis of results included examination for the presence of effusion and crepitus, Lachman and pivot shift testing, and KT-1000 arthrometer testing for side-to-side differences. Subjective analysis consisted of a 15-item visual analog scale completed by patients postoperatively, and pre- and postoperative Tegner and Lysholm scores. The clinical failure rate was 23% (9 of 39) for the female patients and 4% (1 of 26) for the male patients, which was statistically significant. There was also a trend toward increased laxity in female patients. Subjectively, the women also reported a higher frequency and intensity of pain. Based on Tegner activity levels, more of the men returned to their preinjury level of activity than did the women. When compared with the male patients, female patients had a significantly higher failure rate after reconstruction.