&NA;Patients undergoing surgery for herniated lumbar discs were evaluated prospectively with a battery of psychological tests. Personality factors in patients having a good outcome were compared to those in patients having a bad outcome. Both groups had similar surgical findings. Patients with a good outcome were more stable, cautious, efficiently defensive, selfconfident, realistically concerned with their illness, mildly depressed, generally optimistic regarding outcome, and able to withstand setbacks without resorting to emergency reactions. Patients with a bad outcome were less stable, were unpredictable, had inefficient defenses, were more obviously depressed, and were less able to withstand stress and breakdown. However, even the degree of psychological testing used in this study does not definitely predict outcome.