Objective: To assess sensory deficits and their effects on proprioceptive and motor function in patients who had undergone unilateral anterior cruciate ligament (ACL) reconstruction. Design: Four evaluations were conducted: (1) joint position perception of the knee for predetermined angles (0degrees, 15degrees, 30degrees, 45degrees, 60degrees); (2) threshold for detection of passive knee motion at 0degrees, 15degrees, 30degrees, 45degrees, and 60degrees moving into flexion and at 15degrees, 30degrees, 45degrees, and 60degrees moving into extension; (3) latency onset of hamstring muscles; and (4) postural control during upright double- and single-leg stance. Setting: Movement laboratory in Brazil. Participants: Ten participants who had surgical reconstruction of the ACL (reconstructed group) and 10 participants without knee injury (control group). Interventions: Not applicable. Main Outcome Measures: Absolute error, angular displacement, hamstring muscles latency, and mean sway amplitude. Results: Individuals with a reconstructed knee showed decreased joint position perception, a higher threshold for detection of passive knee motion, longer latency of hamstring muscles, and decreased performance in postural control. Conclusions: After lesion and ACL reconstruction, sensory and motor behavior changes were still observed. This may be because of the lack of proprioceptive information resulting from the ACL lesion and/or substitution of ACL by the graft. (C) 2003 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.