Chitinolytic activities were identified in the Protozoa Trichomonas vaginalis. Overall chitinase activity assessed using chitine-azure as substrate was 10.93 +/- 1.21 nmoles/min/mg prot. End nonreducing chitobiosidase (exochitinase) and chitotriosidase (endochitinase) activities were shown using p-nitrophenyl-substrates and had specific activities of 4.55 +/- 0.53 and 0.47 +/- 0.06 nmol/min/mg prot, Kmapp. = 1.32 mM and 5 microM and pH optimum = 7.0 and 6.1 respectively. beta-N-acetylhexosaminidase (NAHase) activity was also detected with a specific activity of 5.40 +/- 0.65 nmol/min/mg prot., Kmapp = 0.656 mM and pH optimum at 7.0. No release of these enzymes into the culture medium was found. The possible role of chitinases in T. vaginalis remains to be investigated.