This paper presents Xfsl, a tool for the automatic tuning of fuzzy systems using supervised learning algorithms. The tool provides a wide set of learning algorithms, which can be used to tune complex systems. An important issue is that Xfsl is integrated into the fuzzy system development environment Xfuzzy 3.0, and hence, it can be easily employed within the design flow of a fuzzy system.This work has been partially supported by the Spanish CICYT Project TIC98-0869 and the FEDER Project 1FD97-0956-C3-02.Peer reviewed