✓ Eighty patients with severe back or leg pain were assessed by a battery of psychological tests. Functional factors (that is, psychological and behavioral characteristics) thought to be contributing to the patient's pain experience were analyzed, and the patient's response to surgery was predicted. Patients were selected for the study on the availability of good follow-up data at 6 months or longer after surgery. The results reveal that the presence of functional factors was not of substantial consideration in the decision for surgical treatment. However, when both the clinical predictions and the subject's response to surgical treatment were rated on the same 0 to 5 scale, it was found that response to surgery could be predicted with 84% accuracy based upon functional data. Few single scores significantly discriminated between success or failure of surgery, and the basis for discrimination was made upon clinical judgment of an array of findings obtained by the functional pain assessment. The results are discussed with regard to a pain model which assumes the presence of an organic-functional pain continuum.