This chapter first gives a brief outline of the most used data mining process. Then, a few successful data mining applications are described, in addition to the some Rough Sets-specific systems. The Rough Sets theory comprises an important genre within the field of data mining, and has been implemented in various applications. Among these are the systems RSES (Rough Set Expert System) , DataLogic/R, KDD-R (Knowledge Discovery in Databases using Rough sets) and LERS (Learning from Examples based on Rough Sets).