1. 1. Key enzymes of oxidative metabolism were assayed in cell-free extracts of the anaerobic protozoan, Trichomonas gallinae. 2. 2. The sole enzyme of the tricarboxylic acid (TCA) cycle detected was malic dehydrogenase. 3. 3. T. gallinae appears to be a TCA cycleless organism that obtains most of its energy from anaerobic fermentation in much the same manner as Tritrichomonas foetus and Trichomonas vaginalis.