Purpose: Most patients with acute low back pain visit emergency room (ER). They mostly need beds, and if their length of stay is longer, it can become difficult to accommodate new patients at the ER. We analyzed the treatment process of patients with back pain and tried to find method for shortening of the length of stay at the ER. Methods: We retrospectively analyzed the medical records of patients with back pain who visited at our ER for one year. Patients were divided into two groups according to their length of stay at ER and were compared the charateristcs of between two groups. Results: A total of 274 patients were included in the study. Eigthy-nine patients (32.5%) were in the group with less than 3 hours and 185 patients (67.5%) were in the other group. In the comparison of the two groups according to the medical departments, the number of patients who were in group with more than 3 hours were 25 (14.0%) in the emergency department, 94 (50.5%) in neurosurgery, 66 (35.5%) in orthopedic surgery. Length of stay was significantly increased in orthopedic surgery and neurosurgery (p=0.014). In addition, the length of stay was longer when computed tomography and magnetic resonance imaging examinations were performed (p=0.000). Regardless of the type of analgesic agent, the median time to the analgesic treatment was shorter in the group with less than 3 hours (p=0.034). Conclusions: In patients with back pain who visit the ER, the emergency medicine doctor will early control the pain and do not unnecessary image examination to reduce a length of stay at the ER.