A liquid chromatographic procedure is described for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, nabumetone, naproxen, piketoprofen, and tolmentin in pharmaceutical preparations. The compounds were separated on a Kromasil C₁₈ analytical column, with a guard column of similar characteristics; the mobile phase was 0.06 M cetyltrimethylammonium bromide, at pH 7, containing 10% 1-butanol. At a flow rate of 1 mL min⁻¹ the elution time of the most retained compound was 23 min. Limits of detection were between 0.01 μ g mL⁻¹ for diclofenac and 0.2 μ g mL⁻¹ for naproxen. The proposed method enables the determination of non-steroidal anti-inflammatory drugs in pharmaceutical preparations. Recoveries were between 95 and 108% of the nominal content declared by the manufacturer and relative standard deviations were <6%.