PURPOSE: This study was performed to determine whether subtle anterior subluxation occurs in anterior cruciate ligament (ACL)-deficient knees with the knee in full extension. TYPE OF STUDY: Radiographic evaluation of tibial position in ACL-intact and ACL-deficient knees. METHODS: Twenty-four subjects with arthroscopically documented ACL-deficient knees were compared with 20 subjects with arthroscopically documented ACL-intact knees. A previously reported method was used to evaluate the tibial position relative to the femur. RESULTS: Measurements on standing lateral radiographs revealed asymptomatic but significant anterior subluxation of the tibia compared with the ACL-intact subjects. CONCLUSIONS: The possibility of anterior tibial subluxation with the knee in full extension should be taken into account when deciding on tibial tunnel placement or when evaluating for postoperative graft impingement by the intercondylar notch.