Experiments were performed on mice to investigate the influences of cimetidine, ranitidine and famotidine on the immune response. Immune response were evaluated by antibody, Arthus reaction (Arthus), delayed type hypersensitivity (DTH), rosette forming cell (RFC), phagocyte activity and whit( blood cell (WBC) in mice, sensitized and challenged with sheep red blood cells (SRBC). The weight of liver, spleen and thymus were measured. Following results obtained in this experiment. 1) The administration of cimetidine as compared to normal group significantly decreased Arthus, Hemagglutinin titer (HA), RFC, DTH, WBC and phagocyte activity, but increased the activity of serum albumin. 2) The administration of ranitidine as compared to normal group decreased RFC and HA. 3) The administration of Famotidine as compared to normal group decreased DTH and RFC, and significantly decreased HA, Arthus and serum protein. 4) The administration of ranitidine and famotidine decreased more humoral immune response than cellular immune response, but the administration of cimetidine significantly decreased humoral and cellular immune response, WBC and phagocyte activity.