Histochemical characterisation of ooplasm and yolk granules in different stages of oocyte maturation in the ovary was made in the freshwater fairy shrimpStreptocephalus dichotomus. In stage I oocyte, the ooplasm is reactive to basic and acidic groups of protein, aromatic groups such as tryptophenyl and tyrosyl and sulphur containing substances. The other organic compounds include acid mucopolysaccharide and acidic lipids. In stage II oocyte, sudanophilic lipoidal substances appear coinciding with yolk formation. Stage III oocytes are characterised by the abundance of yolk granules which are rich in sulphated acid mucopolysaccharide as well as glycogen. Besides these, the presence of acid phosphatase activity in the ooplasm and nurse cell is also noticed and its functional role in relation to vitellogenesis is discussed.