Labeled substrates for 16 different catalytic activities were combined into a cocktail reagent for multienzyme functional profiling, called PHENO-ZYM TM . The assay involves a single reaction followed by determination of substrate consumption by HPLCanalysis. The method allows a rapid identification of multiple enzyme activities, and is compatible with a diversity of growth media and reaction conditions (pH, temperature). The PHENOZYMTM cocktail was used to analyze the activity of 16 enzyme activities in a series of microbial strains, including thermophilic microorganisms. The functional profiles were used for a functional classification of the different microbial strains tested by hierarchical cluster analysis. The resulting "phylo-enzymatic" tree revealed associations consistent with the known phylogenetic classification of the strains. The influence of the culture medium on the enzyme activity profiles was also apparent.