Fuzzy logic replaces inflexible bivalent logic and complicated mathematical functions with simple linguistic rules. The models based on these rules can be constructed using relatively little mathematics, and exhaustive computer calculation can be replaced with easily manageable computer programs. Fuzzy logic can actually be used to create models that cannot be constructed using other methods. The purpose of the FuzzyFluid program is to visualise the use of fuzzy logic in an expert system developed to interpret cerebrospinal fluid, which can be used in normal laboratory procedures, especially in the field of pathology. The program requires information about cytological findings as well as data on glucose concentration and protein levels. The FuzzyFluid program interprets the input values initially using fuzzy logic and subsequently using Boolean logic before finally printing a report.