Low back pain (LBP) is a leading cause of disability in working age adults. Several studies suggested that the role of paraspinal muscles in LBP. The paraspinal muscles demonstrated some degree intramuscular fatty infiltration as a form of atrophy. This is a study to assess the paraspinal muscles fatty infiltration from lumbosacral MRI in patients with acute and chronic LBP. Total sample of 52 LBP patients, with exclusion criterias as history of trauma, infection, spine surgery, malignancy, bedridden for at least 1 week within the last 12 months, immunodeficiency, sepsis, burn, congestive heart failure, chronic renal disease, and history of liver, gallbladder, or pancreatic disease. The grading assessment were using Goutallier classification, a reliable tool to assess fatty infiltration grade in erector spinae, multifidus, and psoas major. The result showed that acute LBP patients (n=23) have lower maximum grade of fatty infiltration (grade 1 in erector spinae; grade 2 in multifidus and psoas major). While the chronic LBP patients (n=29) have higher maximum grade of fatty infiltration. We also found that the lowest level tends to showed higher grade of fatty infiltration in all three muscles. However, it needs a further study to evaluate association between duration and grade of fatty infiltration, or to determine whether the fatty infiltration occurred before LBP or vice versa.