Vitellogenesis in Orientocreadium batrachoides, an intestinal parasite of the catfish, Clarias gariepinus was investigated by transmission electron microscope. Four stages of vitellocyte development have been distinguished during vitellogenesis: (I) stem cell stage of the gonial type (immature vitellocyte), (II) early and (III) advanced stages of maturing vitellocytes. Both early and advanced stages of maturing vitellocytes involved the initiation of protein synthetic activity, onset of shell globule formation and progressive fusion of single shell globules into large shell globule cluster in their cytoplasm and (IV) mature vitellocyte. Vitellocyte maturation is characterized by: (1) an increase in cell volume, (2) extensive development of parallel cisternae of granular endoplasmic reticulum, (3) development of Golgi complexes and (4) a continuous development of shell globules that fused into shell globule clusters. Mature vitelline cells are characterized by shell globule clusters, which play an important role in egg shell formation, lipid droplets and β-glycogen that accumulated in large amounts in their cytoplasm. Single “lamellar” granules are present in the cytoplasm of the mature vitellocytes.