The effect of vitamin A on the immune response in ICR mice was studied. The effects were evaluated by immuno organ weight, peripheral circulating white blood cells, HA and HY titer, peritoneal exudate cells, RFC, Arthus reaction and DTH in mice. The spleen of mice was significantly hypertrophied by deficiency or over doses of vitamin A as compared with control group (50IU/kg). Arthus reaction, RFC and peritoneal exudate cells were sharply decreased according to the increase of vitamin A doses. The number of white blood cell was decreased according to the increase of vitamin A doses, but in the case of vitamin A 50,000 IU/kg treated group, it was significantly increased. These results suggest that deficiency or over dose of vitamin A decrease humoral and cellular immune response.