Introduction. Low back pain (LBP) is a most frequent ailment reported by patients to the doctors. This pain results from static and dynamic overloads and low physical activity. LBP increases degenerative changes and leads to the reduction of the range of motion (ROM), daily activity and occupational life. LBP is also a social and either economical problem as well. The aim of the study was to assess the influence of TENS application on the pain intensity and blood level of endogenous opioids in patients with LBP. Material and methods. The study group consisted of 33 patients (22 women and 11 men) with LBP, which were qualified to the study on the basis of medical diagnosis defined by physician. The physical therapy consisted of 10 TENS applications, performed every consecutive days by 15 minutes. Before and after treatment the spine ROM was examined by Schöber test, the blood samples were taken from all participants. Before and after TENS applications the patients were asked to fill up the questionnaires: Oswestry Disability Index (ODI), Roland Morris Disability Questionnaire (RMDQ) and Visual Analogue Scale (VAS). The results therefore underwent statistical analysis. Results. Analysis of correlation between change in the level of pain and ODI has evidenced that pain reduction is accompanied by significant increase of patient’s physical efficiency (p<0,05). The improvement of the spine ROM in the study group was also observed (flexion by 67%, extension by 10%) as the result of TENS treatment. The significant decrease of concentration of cortisol from 41,91 to 32,49 ng/ml and significant increase of ß-endorphin blood level from 12,26 to 14,54 ng/ml have been found after TENS application. Conclusions. TENS therapy in patients with low back pain increases spine range of motion, improves patient’s physical efficiency and decreases intensity of pain.