Three types of circulating haemocytes have been identified in the haemolymph of the Indian white shrimp, Fenneropenaeus indicus, by electron microscopy. The ultrastructure of an agranulocyte, a dense granulocyte, and a semi-dense granulocyte, are described. The possible presence of a fourth type of haemocyte, viz., the cyanocyte, is discussed. The ultrastructure of a special type of haemocyte found in the haemolymph of shrimps with a developing ovary is described.