Alkylglycerols (AG) are glyceryl ether lipids and are present in human and cow's milk and the hematopoietic organs such as bone marrow, spleen, and liver. The bio-logic effects of AG include stimulation of blood leukocyte and thrombocyte production and activation of macrophage and anti-tumor activity. The present study was conducted to determine the effects of dietary AG in lactating rats on AG levels in milk and development of certain immune responses in the pups. Lactating rats were fed diets supplemented with various levels of AG. Milk samples were expressed from the dams and blood was collected from the pups on postpartum d 8, 16, and 24. Concentrations of AG in milk from the dams fed AG were significantly greater than those of the controls (p< 0.05). Peripheral blood granulocytes were significantly elevated in pups from the dams fed AG, but there were no differences in peripheral blood lymphocyte numbers. Plasma levels of immunoglobulins were significantly greater for IgG (p< 0.01) and IgM (p< 0.001) in pups from the dams fed AG than in the control pups. The supplementation of AG in the diets of lactating dams significantly elevated AG levels in the milk, and the increased AG in the milk subsequently stimulated certain immune responses in the pups.