Using data from the Second National Acute Spinal Cord Injury Study (NASCIS II), the authors sought to characterize the role of surgery in the management of traumatic spinal cord injury and to examine the interaction between pharmacological treatment and surgery. Patients who did not undergo surgery had more severe spinal cord injuries initially than those who had surgery. However, no differences in neurological improvement at 1-year follow-up were found between those who underwent surgery and those who did not. The results suggest that either early surgery (< or = 25 hours after injury) or late surgery (> 200 hours) may be associated with increased neurological recovery, particularly motor function, but these results are equivocal. Surgery was not shown to interact with pharmacological treatments, indicating that the effect of drug treatment in NASCIS II, reported elsewhere, is not influenced by surgery. Other independent variables that best predicted improvement in motor score were age of 25 years or younger, incomplete injury, and lower baseline emergency department neurological scores. This study does not provide clinically relevant evidence concerning the efficacy of timing or the value of surgery in treating patients with spinal cord injuries. A randomized study on the timing and efficacy of spinal cord surgery is needed to obtain valid comparisons of the efficacy of surgical treatments.