PURPOSE: The effect of double-bundle ACL reconstruction on knee kinematics has recently been studied by several authors under controlled laboratory conditions however little evidence has been derived from dynamic in vivo evaluations. This study hypothesized that tibial rotation during pivoting motor tasks would be better restored after double-bundle ACL reconstructions when compared with single-bundle procedures. METHODS: Twenty patients with a chronic ACL rupture were randomly assigned to receive a single- or double-bundle ACL reconstruction. Both knees were evaluated pre-operatively by kinematic 3-D gait analysis while performing low- and high-demand motor tasks, including pivoting. At 6 months post-operatively, measurements were repeated in 16 patients. Ten healthy, sex- and age-matched subjects with no history of lower limb pathology formed the control group. The tibial rotational excursion was set as the dependent variable. RESULTS: The results indicate that at 6 months after surgery both "anatomic" single- and double-bundle ACL reconstruction are able to restore tibial rotational excursion when compared with the contralateral knees and with control knees from uninjured subjects. Chronic ACL-deficient patients show an increase in tibial rotation in both knees during high-demand pivoting tasks. CONCLUSIONS: Both "anatomic" single- and double-bundle ACL reconstruction adequately restore tibial rotational excursion in a human, "in vivo" kinematic model. As knee stability measurements by in vivo kinematic 3-D analysis more accurately represent actual knee loading during activities, the results of this study might better correlate with functional outcome after ACL reconstructions compared with static knee stability tests or ex vivo laboratory experiments. In such, the results of this dynamic study do not support the theoretical advantage of a double-bundle ACL reconstruction over an "anatomic" single-bundle ACL reconstruction. LEVEL OF EVIDENCE: II.