The objective is to study the efficacy and safety of nimesulide (nemulex) in the treatment of acute low back pain (LBP). The medical documentation of 54 patients with primary syndrome of LBP, which were treated in a polyclinic with nemulex at a dose of 200 mg per day had been studied. The assessment of patients’ condition and efficacy and safety of the treatment was conducted based on the information after three visits (1-st, 5-th and 10-th day). The analysis took into account the data of clinical-neurological examination and the assessment of pain intensity at rest and at movement according to the visual analogue scale (VAS) and the severity of Lasegue symptom and limitation of movements in the lumbar spine. Safety of the therapy was evaluated on the basis of accounting of undesirable side reactions and data analysis and physical examination and laboratory testing. Cardiovascular safety was assessed by blood pressure and blood lipid profile on day 10. The use of nemulex at a dose of 200 mg per day resulted in relief of pain and increase of mobility in the lumbar spine on the 5th day of treatment that indicates the effectiveness of anti-inflammatory therapy to restore the previous functional status of patients with LBP. The use of nemulex was accompanied not only by statistically significant analgesic effect (0,78±0,14 points alone; 1,12±0,18 points when moving by VAS on the 10th day of the treatment) and high security (only 1 of the 54 patients was recorded to have elevation of hepatic transaminases; and 2 patients with dyspepsia without endoscopic changes of gastrointestinal tract).