This study examines the effect of intake of oral contraceptive steroid in S. mansoni infected mice as regards parasitological, biochemical, histopathological and ultrastructural changes. Three groups were studied group I: S. mansoni infected mice received contraceptive pills six weeks post-infection (p.i.), group II: S. mansoni infected control and group III: non-infected control. Administration of oral contraceptive pills to S. mansoni infected mice results in significant reduction in tissue egg count with a high percentage of dead eggs as observed in the oogram study. There was statistically significant increase in all parameters of the hepatic functions except the prothrombin activity which showed significant decrease. Histopathological examination revealed less cellular granulomas with marked fibrosis, foci of hyperplastic changes in the liver cells and accentuation of cellular degenerative changes. On the subcellular level, there were marked proliferation and dilatation of rER and SER, evident increase of ribosomes, alteration in mitochondrial cristae with intra luminal inclusions and increase glycogen content of hepatocytes.