OBJECTIVE: To evaluate the effect of compensation or secondary gain on the pain behavior and psychometric characteristics. METHOD: We examined 88 patients who complained of chronic low back pain by the various pain questionnaires, electrodiagnostic study and magnetic resonance imaging (MRI). Total patients were classified into two groups (46 patients who wanted disability evaluation and 42 patients who did not). RESULTS: Mean score of visual analogue scale, total sum of McGill pain questionnaire and pain rating index on sensory, affective and miscellaneous dimensions were significantly higher in patients related to disability compensation than those in patients without compensation. Mean scores of pain disability index and symptom checklist-90-revision were significantly higher on various subclass in patients with compensation. Various pain scales were significantly correlated to each other in both group but the severity of electrodiagnostic study and MRI findings were not related with the degree of pain index score in both group. CONCLUSION: Compensation or secondary gain affect pain behavior and psychometric characteristics in chronic low back patients. So when we evaluate or treat the patients with chronic low back pain, we should consider above results.