Thiamine pyrophosphatase and nucleoside diphosphatase have been studied histochemically in Raillietina (Raillietina) johri. Thiamine pyrophosphatase activity has been observed in the tegument, subtegumental muscle, subtegumental cells, medullary parenchyma, excretory canal and various reproductive structures like testes, ovary, vas deferens, spermatozoa and vitellaria. Eggs exhibit moderate enzyme activity. Various nucleoside diphosphates have been found to be hydrolyzed by thiamine pyrophosphatase. CaCl2, MgCl2 and MnCl2 each activated the enzyme at a final concentration of 6 mM whereas cysteine, reduced glutathione and PCMB inhibited the enzyme activity at a final concentration of 10 mM, 10 mM and 20 mM, respectively. KCN and NaF had no effect on the enzyme staining at concentration as high as 50 mM and 30 mM, respectively. Possible roles of the enzyme in the parasite have been discussed.