Abstract: The present paper reports a series of experiments on the influence of tartar emetic, F30066, cucurbitine (a new amino acid isolated from Cucurbita moschata Duch. var. melonaeformis Mark), hemerocallin (an active principle of Hemerocalli thunbergii Baker), dipterex or rosaniline on glutamic-pyruvic transaminase(GPT) and glutamic- oxaloacetic transaminase(GOT) of schistosomes.It was found that when drugs were added to the homogenates of the worms, tartar emetic and cucurbitine had an inhibitory effect on GPT. When the final concentration of tartar emetic was 2×10^-4M and that of cucurbitine was 5×10^-2M, the extent of inhibition amounted to about 50%. Simul- taneously, cucurbitine showed a weak enhancing effect on GOT. On the contrary, F30066 exerted a weak inhibitory effect on GOT but no effect on GPT. Other compounds did not show any effect on either enzyme. In order to explore the effect of the schistosomacides on the GPT and GOT of the worms maintained in culture medium, the parasites were kept in Tyrode's solution con- taining the drugs. After 1 and 4 hours of incubation, the worms were removed from the medium and homogenized for the determination of its GPT and GOT. When the final concentration of tartar emetic in the medium reached 10^-3M, the activity of GPT in Schistosoma japonicum was also decreased to about 50%.When schistosomes were placed in Tyrode's solution containing 2×10^-4 M of F30066 for 4 hours, the activity of GPT was decreased to 25%, while no effect on GOT of the worms was observed. In order to investigate the in vivo effect of the drugs, infected mice were treated with the schistosomacides at the dosage of 1/2 LD₅₀ for 5 days. The worms were re- moved each day from 3-5 mice and homogenized as quickly as possible for determining its activity of GPT and GOT. During the treatment, it was apparent that the worms decreased in size and their reproductive organs were degenerated, but no appreciable change in the activity of GPT or GOT was observed. It was concluded that the anti- schistosomal activity of the drugs tested had no effect on the metabolic sequences which were catalysed by GPT or GOT.