Positive effect of aerobic exercises in chronic low back patient is shown recent studies. But it is unknown that which type walking pattern is more effective. The aim of this study is to assess effectiveness of over ground and treadmill walking in chronic low back pain patients and compare them. This is a randomized-prospective study. After screening 72 chronic low back pain patients, 18 met qualification criteria for this study. Patients were assessed in terms of physical examination findings, exercise tolerance test parameters. The Visual Analogue Scale (VAS) was used to assess the patients pain. The life quality of patients was assessed by Short Form-36 (SF-36). The mobility of the spine was assessed by single inclinometer measurement, Schober test and fingertip-to-floor test. Patients were randomized to two groups as over ground and treadmill walking. Conventional therapies were applied to both groups in same way. One group has taken treadmill and other has over ground walking exercise for 4 weeks and 3 times a week under supervision. Patients were assessed before and after treatment. As result, in the over ground walking group, there was statistically significant improvement in T12 and real extension values (p=0,005 and p=0,010). The improvement of real extension values were significantly higher in over ground walking group than treadmill walking group (p=0,018). The improvement at the MET levels in treadmill walking group was statistically significant (p=0,004). However, there was no statistically significant difference between two exercise groups. There were statistically significant decreases at the Oswestry disability scores in the over ground walking group before and after therapy (p<0,001). Walking exercise in addition to conservative treatment can improve pain, disability and psychological status in patients with chronic low back pain. In this study we found that over ground walking is more effective than treadmill walking at reducing disability due to low back pain.