Abstract: Rough sets theory is a new mathematical tool to deal with vagueness and uncertainty. Its soundness and usefulness has been proved in many real-life applications. The main problems that can be approached using rough set theory include data reduction, discovery data dependencies, generation of decision (control) algorithms from data, and so on. Hence it is a promising soft computing methodology. In this paper, the basic concepts of the rough sets theory is briefly introduced, and some applications of this theory are also discussed.