Despite the higher incidence of anterior cruciate ligament (ACL) injuries in female than in male athletes few authors have studied the effects of gender on the outcome of ACL reconstruction. This prospective study compared the results of ACL reconstruction using the patellar tendon and hamstring techniques in men and women. We prospectively followed 80 comparable athletes (46 males, 32 females) from a population of 287 patients operated on at our institution for ACL reconstruction using either patellar tendon or hamstring graft. There were 26 males and 14 females in the patellar tendon group, and 22 males and 18 females in the hamstring group. All patients were operated on by the same surgeon within 6 months from injury and underwent the same rehabilitation program at the same center. After an average of 36 months the patients were assessed by clinical evaluation, computerized knee laxity analysis, and isokinetic and functional strength tests; standard knee scores were also used. Among patellar tendon patients there were no significant differences between males and females regarding knee evaluation form, laxity, or isokinetic and functional tests. Females in the hamstring group had significantly greater laxity, and isokinetic tests at 1 year revealed a significantly higher deficit of peak torque at 60 degrees /s in flexion and extension. We suggest further studies on the clinical significance of these findings particularly on their possible ramifications in the areas of return to sports and rehabilitation of female athletes.