In the recent years microemulsions have attracted a great deal of attention not because of their importance in industrial application but also their intrinsic interest. Microemulsions are colloidal dispersions composed of an oil phase, aqueous phase, surfactant and cosurfactant at appropriate ratios. Microemulsions are an attractive technology platform for the pharmaceutical formulators as it has excellent solubilisation properties, transparency and the relatively simple formulation process.Microemulsions are an attractive technology platform for the pharmaceutical formulators as it has excellent transparency and the relatively simple formulation process. The role of microemulsion systems is of paramount importance in providing novel solutions to overcome the problems of poor aqueous solubility of highly lipophilic drug compounds and provide high, more consistent and reproducible bioavailability. The 5-fluorouracil topical microemulsions were formulated and the different compositions of components were obtained by constructing pseudoternary phase diagrams. Their concentrations were optimized after the evaluation of their effect on permeation of drug.