p-Cresol was repeatedly detected as a trace metabolite in anaerobic slurry reactors treating 2,4,6-trinitrotoluene (TNT)-contaminated soils. This study shows thatp-cresol was not a metabolite of the anaerobic degradation of TNT, by using a combination of analytical techniques and13C-labelled TNT. Instead,p-cresol, an intermediate in the degradation pathway of some amino acids, was shown to be inhibited by TNT and its metabolites. The range and persistence of inhibition top-cresol microbial degradation decreased with the level of amino-substitution of the derivatives. This explains whyp-cresol accumulated within the TNT-treating anaerobic bioslurry, as it could not be further biodegraded in the presence of TNT.Key words:p-cresol, bioremediation, trinitrotoluene, inhibition, metabolites.