Abstract: | The splenomegaly assay (Simonsen, 1962) was standardized using different strains of rats and mice. Male Wistar rat (donor)-female Swiss mouse (host) was found to be the suitable combination that could be employed in subsequent experiments to study the potential of contraceptive steroids to alter CMIR. The index of splenomegaly appeared to increase in case of mice treated with combination oral contraceptives (Ovulen, Ovral or Enovid). The differences observed, however, neared significance only in the case of Ovral (0-05 less than P less than 0-1). Neither chlormadinone acetate nor megestrol acetate significantly altered the index of splenomegaly. |