The response of 111 chronic low back pain patients to a comprehensive behavioral treatment program emphasizing relaxation procedures is examined. Over the course of treatment, significant reductions were obtained on measures of subjective tension, EMG activity, and pain. Many patients also decreased their intake of analgesic/narcotic agents and reported an increase in activity level. In order to examine individual differences in pain relief, the 28 patients who had the greatest decreases in pain were compared to those who had the least decreases in pain. Patients who had the best outcome in terms of pain relief were significantly more likely to show improvements in other outcome measures. In addition, these patients rated their pain initially as more severe, had continuous pain for fewer years, and were less likely to be on disability or to have had multiple surgical procedures. These results are discussed in the light of recent data from other behavioral treatment studies with chronic low back pain patients and implications for behavioral assessment and treatment are discussed.