The adult trematodes, Fasciola hepatica, Eurytrema pancreaticum and Paramphistomum cervi, employed in this experiment were obtained from the cattle slaughtered at the local abbatoir. The worms selected and washed several times in normal sterilized saline solution. Each about ten of intact F. hepatica, fourty of E. pancreaticum, and twenty of P. cervi were incubated in 50 cc volume of special incubation flasks with incubation medium consisting of 10 cc. of Krebs-Ringer phosphate buffer(pH 7.4) The incubation medium was added C(14)-1-acetate and non-radioactive carrier Na-acetate so as to contain acetate concentration of 50 mg per cent. The worms were allowed to incubate for 5 hours in the Dubnoff metabolic shaking incubator at 38 degrees C. After incubation period, respiratory CO2 samples from central well of incubation flask were analysed for total CO2 production rate and their specific activity of respiratory CO2. The lactate and pyruvate appearance rates were determined by analyzing the lactate and pyruvate concentration in a medium after incubation. The glycogen samples isolated from worms were analyzed for the tissue concentration and their radioactivities in order to determine the turnover rate of glycogen pool. Radioactivities of these series of experiments were counted by an endwindow Geiger-Muller counter as an infinitely thin samples. The quantitative analysis of C(14)-acetate utilized by F. hepatica, E. pancreaticum and P. cervi were compared and discussed in this report. According to these data of the experiment, it is suggested that the fatty acid such as acetate may play a part of their oxidative process into the respiratory CO2 and the synthetic process into glycogen in the above species of trematodes.