A large sample of patients with chronic low back pain were studied on admission to a behaviorally oriented in-patient pain program, at program completion, and at 1 month follow-up. Cluster analysis of admissions MMPI scores were used to identify 4 patient subgroups each for males and females. There were no subgroup differences found on any of the admissions demographic, pain report, or physical function measures, or differential treatment outcome based on subgroup. All groups began with high levels of pain and disability, yet improved dramatically following treatment. There was a general normalization of the MMPI reflected by elevated MMPI scales found at admission showing significant decreases at follow-up testing. Subgroups derived from follow-up MMPI testing were related to physical functioning at follow-up and pain report measures, with the elevated subgroups showing higher levels of continued pain and disability.