Background: This study was conducted to determine the frequency of abnormal discal findings in lumbar MRI in patients with non traumatic non surgical low back pain who referred to Imam-Khomeini hospital Materials and methods: This study was conducted as a descriptive – analytical cross-sectional prospective survey among 280 consecutive patients who referred to Imam-Khomeini hospital in 2008 -2009. The data were collected by check list and analysis was done by SPSS 10 Results: The mean age of the patients was 40.98. 56.1% were female Abnormal MRI was seen in 83.2% and 72.9% had disc involvement including 40.7% central, 21.1% right and 36.3% left involvements, 25.75% had bulging, 62.85% protrusion, 11.05% extrusion and finally 0.35% had sequestration. Conclusion: It may be concluded that disc protrusion and bulging are the most common findings in MRI and according to excellent ability of MRI in diagnosis of herniation, MRI is recommended in patients with non surgical non traumatic low back pain.