Introduction: Anterior cruciate ligament (ACL) injuries are one of the most common traumatic injuries among physically active. ACL injuries are the largest isolated problem in orthopedic sports medicine. Many studies have found that a previous injury of the lower limb itself causes an increased risk of a new knee injury. To evaluate rehabilitation after ACL reconstruction and to assess whether the active is ready to return to sport a combination of strength tests, functional jump tests and any form of self-assessment score are generally used. The person must achieve 90-100 % of the non-operated leg function to be approved as ready to return to sport. To maintain good knee function, it seems to be important to continue specific training for the operated leg even after return to sport. Purpose: To investigate the difference in strength and in jump-performance that exists between the operated and non-operated leg, four to seven years after ACL-reconstruction. Method: Seventeen subjects who have undergone ACL reconstruction four to seven years ago were included in the study. Strength in quadriceps and hamstrings were measured by one repetition maximum, and jump performance were measured in one-legged long jump test. Comparisons were made for the operated and non-operated leg. Results: Operated leg performed with significantly lower than the non-operated leg. For the quadriceps, the operated leg performed on average 45 (SD13) kg compared to 57 (SD13) kg in non-operated leg. The difference was significant (p=0,047). Hamstrings in operated leg performed on average 28,8 (SD 6) kg compared with 38,6 (SD7,5) kg in non-operated leg, the difference was significant (p=0,030). In the one-legged long jump test, the operated leg performed in averaged 131 (SD 20) cm compared with 151(SD 18) cm in non-operated leg, the difference was significant (p=0,021). Conclusion: ACL-reconstructed subjects who achieved satisfying results after rehabilitation seems to impair in knee function in the operated leg regarding strength and jump-function 4-7 years after ACL-reconstruction.