Dexketoprofen, the active enantiomer of the racemic compound ketoprofen, is a new nonsteroidal antiinflammatory drug (NSAID) of the arylpropionate family. The efficacy and safety of dexketoprofen trometamol were compared with the equivalent enantiomeric dose of ketoprofen in a multicenter, randomized, double‐blind 3‐week trial of adult outpatients with pain due to osteoarthritis of the knee. After a washout period of 7–15 days, patients were randomly assigned to receive either dexketoprofen trometamol 25 mg tid (N = 89) or ketoprofen 50 mg tid (N = 94). Of the 183 patients enrolled, two were lost to follow‐up. At the end of treatment (3 weeks), the main efficacy outcome measures were significantly better in the dexketoprofen trometamol group than in the ketoprofen group. In addition, overall physician assessment indicated that 75% of the dexketoprofen group had improved compared with 50% of the ketoprofen patients. There were fewer adverse events in the dexketoprofen treatment group, but the difference did not reach statistical significance. These results demonstrate that dexketoprofen trometamol 25 mg tid is more effective than ketoprofen 50 mg tid in short‐term symptomatic treatment of knee osteoarthritis and suggest that the tolerability of dexketoprofen trometamol is more favorable than ketoprofen. Therefore, the substitution of dexketoprofen for racemic ketoprofen may be advantageous in clinical practice.