BACKGROUND, METHOD: The analgesic efficacy and tolerability of dexketoprofen-trometamol (DKPT) was compared with tramadolhydrochloride (TRAM) in a multicentre, randomised, double-blind, clinical trial in 192 Patients with acute low back pain. The initial pain at rest and on movement should be at least 50 mm on a 100 mm visual analogue scale. The daily dose during the 7 days' treatment was 50 mg TRAM t.i.d. (n = 95) or 25 mg DKPT t.i.d. (n = 97). The patients were allowed to take additional Paracetamol up to 4 x 500 mg per day as rescue medication.From the 4th day of treatment pain on movement decreased significantly (p = 0.044) in the DKPT-group in comparison with the TRAM-group. The nocturnal pain decreased during the treatments with a difference in therapies of 22.9% in favour of DKPT. Within the DKPT-group the patients required additional Paracetamol more often only during the 1st day of treatment whereas the patients of the TRAM-group required the additional rescue medication mainly during the first 3 days of treatment. This difference was statistically significant (p = 0.011). Under DKPT treatment patients experienced significantly less adverse events (with an at least "possible" causal relationship; p = 0.026). This can be explained by central nervous disturbances that occurred only in the TRAM group. The distribution of gastro-intestinal disorders was identical in both treatment groups.With this results DKPT in comparison with TRAM also showed to be a strong analgesic drug with a better risk-benefit relation due to its better tolerability.