In this study, nimesulide which has been used as an analgesic, antipyretic and anti-inflammatory agent, was analyzed: by using second order derivative UV spectrophotometry; The solvent, the degree of derivation, ranges of wavelength and n-value were chosen in order to optimize the conditions. The concentration of nimesulide in its solutions in ethanol and chloroform were determined between the wavelength ranges of 200 and 500 nm (n = 6, Delta lambda = 21) and in the linearity ranges of 2.0-90.0 mu g ml(-1) in ethanol and 2.0-50.0 mu g ml(-1) in chloroform by using the values obtained from the second derivative UV spectrum of the substance. The developed second derivative UV spectrophotometric method was applied to the pharmaceutical preparations such as tablet, sachet (granule) and suspension. Tablet and sachet were analysed in ethanol while the suspension was analysed in chloroform. The results obtained: from derivative UV spectrophotometry were compared with those obtained by using HPLC. It was found that the difference was not statistically important between these methods. It was concluded that developed derivative UV spectrophotometric method was accurate, sensitive, precise: reproducible and could be applied directly and easily to the pharmaceutical preparations. (C) 2000 Elsevier Science B.V. All rights reserved.