Pregnancy caused a significant increase (P less than 0.001) in the ascorbic acid and cholesterol concentrations in the spleen as compared to the controls, indicating a rise in its metabolic functions. When thyroid gland was removed either from the non-pregnant animals or at different stages of gestation from pregnant animals, there were significant (P less than 0.001) fall in the levels of these biochemical parameters as compared to the corresponding intact groups. These findings indicated that splenic functions undergo certain changes during pregnancy and the thyroid hormones significantly influence them.