Crystal structures of two nimesulide derivatives, C13H14O3N2S (2) and C21H16O5N2S (3), have been determined from X-ray powder diffraction data and their electronic structures were calculated at the DFT level. The optimized molecular geometries of 2 and 3 correspond closely to that obtained from the crystallographic analysis. Intermolecular hydrogen bonds and pi...pi stacking interactions form supramolecular assembly in both compounds. The HOMO-LUMO energy gap (> 2.2 eV) indicates a high kinetic stability of both compounds. Although the compound 2 does not exhibit any anti-inflammatory activity, 3 can induce 34% edema inhibition in rat paws. (C) 2010 Elsevier B. V. All rights reserved.