Simplification is an important step in the design of a fuzzy system since the membership functions that represent the fuzzy sets as well as the 'if-then' rules that relate them usually contain redundant information. This paper presents a CAD tool which provides the user with a wide set of algorithms to automate simplification process. It allows reducing the number of membership functions and rules described initially as well as increasing its expressiveness and linguistic interpretability. Since the tool is included within the design environment Xfuzzy 3, the simplified system can be also verified, tuned and synthesized automatically. Several examples are included to illustrate the efficiency of the simplification facilities provided. © 2006 IEEE.