OBJECTIVE: To verify the effect of thermo-undulation therapy on the patients with chronic low back pain. METHOD: 115 patients with back pain (mean age: 51.2 year-old; male, female: 46, 69) were recruited. Experimental group (n=85) was subjected to thermo-undulation therapy for 30 minutes, once a day, five days a week during eight weeks and control group (n=30) was administered with sham procedure. Before and after the therapy, range of motion (ROM) the spine and flexibility of lower extremity muscles were evaluated with goniometry. The functional status was measured by Roland Morris disability questionnaire and quality of life was measured by the SF-36 (36-Item Short Form Health Survey Instrument) and SF-12 scales. The STAI-6 (Spielberger State-Trait Anxiety Inventory) was used for anxiety. We checked the intensity of pain by visual analog scale (VAS) and evaluated the effect of far-infrared ray with Digital Infrared Thermographic Imaging (DITI) technique. RESULTS: After therapy, the scores of muscle flexibility, spine ROM, VAS, Roland Morris disability questionnaire, SF-36, SF-12 and STAI-6 showed a tendency to improve in experimental group (p<0.05), but no significant differences compared with control group (p>0.05). Only the temperature differences of experimental group by DITI were significantly lower than those of control group (p<0.05). CONCLUSION: Thermo-undulation therapy may be an adjuvant therapy for chronic low back pain.