Proprioception of the knee was measured in 20 patients with reconstructed anterior cruciate ligaments and in 19 age-matched controls. The mean time from surgery was 2 years. Three tests of proprioception were used: (a) threshold to detection of passive motion from 20 and 40 degrees toward flexion and extension, (b) active reproduction of a 30 degrees passive angle change, and (c) visual reproduction of a 30 degrees passive angle change. The aim was a complete, bilateral, proprioceptive evaluation of patients who had undergone reconstruction of the anterior cruciate ligament. As compared with those in the control group, the knees with reconstructed anterior cruciate ligaments had a higher threshold to detection of passive motion in the extension trials from 20 and 40 degrees (p = 0.0003 and 0.04, respectively) and in the flexion trials from 20 and 40 degrees (p = 0.004 and 0.0008, respectively). When the uninjured knees of the patients were compared with those in the control group, higher values for threshold to detection of passive motion were found in the flexion trials from 20 degrees (p = 0.002) and 40 degrees (p = 0.02). Thus, decreased proprioceptive ability was present in some measurements of these patients after reconstructive surgery, not only in injured knees but also in uninjured knees, as compared with the reference group. The functional relevance of these findings was not investigated in this study, but the results suggest that bilateral proprioceptive considerations should be made when evaluating prognostic factors, treatment, and risk of contralateral knee injury in patients with reconstructed anterior cruciate ligaments.