The influence of several penetration enhancers alone and/or in various combinations on the percutaneous penetration of nimesulide (NM) from Carbopol(R) 934 based gel formulations was investigated. Skin permeation studies were performed using Franz-type diffusion cells and full-thickness abdominal rat skin. Various types of compounds such as ethanol, isopropyl alcohol, propylene glycol, Transcutol(R), Tween(R) 80 and oleic acid were employed as penetration enhancers. The steady-state flux, the lag time and permeability coefficients of NM for each formulation were calculated. The results showed that the skin permeability of NM from gels tested was significantly increased (P < 0.05) by isopropyl alcohol (40%) and the combination of oleic acid (3%) with Transcutol(R) (30%) when compared with the control formulation. In conclusion, these substances could be considered as penetration enhancers for NM topical formulations.