Experiments were performed on mice to investigate the influences of doxycycine and ethanol on the immune responses. Doxycycline was injected intraperitoneally and ethanol was administered in the drinking water. Mice were sensitized and challenged with sheep red blood cells. Immune responses were evaluated by humoral immunity, cellular immunity, peripheral circulating white blood cell and phagocyte activity. Pathotoxicological influences were measured by serum protein and albumin. The weight of spleen, thymus and liver were measured. Doxycline and ethanol combined administration decreased the weight of thymus and spleen. Humoral and cellular immune response were reduced by doxycycline administration. Especially ethanol combined administration significantly reduced humoral and cellular immune response. Phagocyte activity was increased by ethanol combined administration and peripheral circulating white blood cell was significantly increased by ethanol adminstration. Ethanol combined administration decreased serum A/G ratio.