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Production of ammonia is difficult to find among the various studies of amino acid metabolism in protozoa. Several studies suggest that catabolism of arginine to ammonium is important for the growth of trichomonads. Trichomonads are amitochondriate zooflagellates that thrive under microaerophilic and anaerobic conditions. We were able to detect accumulation of ammonium ions and ammonia in cultures of Tritrichomonas foetus and Trichomonas vaginalis including those resistant to metronidazole. Ammonium ions and ammonia were detected using the indophenol colorimetric method. Aerobic overnight cultures had 0.9 mM of soluble ammonium (NH4+ and NH3) or a 20% greater concentration of ammonium relative to sterile tryptose, yeast extract maltose medium with heat inactivated horse serum that was incubated similarly. Production of ammonia itself was confirmed by analysis of a wick that was moistened with sulfuric acid (40 mM) and placed above the liquid in sealed cultures of a strain of T. vaginalis. The wicks from these cultures captured the equivalent of 0.048mM of volatile ammonia (NH3) from the liquid as compared to 0.021mM volatile ammonia from sterile medium after overnight incubation. Intact cells of trichomonads (0.1mg protein) incubated in Doran’s buffer and with or without (1 mM) L-arginine produced significant amounts of soluble ammonium (0.07 mM, 0.035 mM respectively) during 60 minutes. These amounts are similar to those reported for the metabolism of carbohydrates by trichomonads. The results indicate that ammonium ions and the more irritating ammonia are significant metabolites of trichomonads.