The FuzzyJ Toolkit, originally developed at the National Research Council of Canada, is a set of Java(tm) classes that provide the capability for handling fuzzy concepts and reasoning. It is hoped that this proves useful for exploring the ideas of fuzzy logic and fuzzy reasoning in a Java setting. Much of the work is based on earlier experience building the FuzzyCLIPS extension to the CLIPS Expert System Shell. The toolkit’s API can be used standalone to create fuzzy rules and do reasoning, however, it can also be used with Jess, the Expert System Shell from the Sandia National Laboratories. The integration with Jess, FuzzyJess, provides a capability that is similar to but in many ways more flexible than FuzzyCLIPS.