The effect of rancid perilla oil on the immune response in mice was studied. ICR male mice were divided into 5 groups and were fed on the experimental diets for 4 weeks. Mice were sensitized and challenged with sheep red blood cell. Immune responses were evaluated by antibody production, Arthus reaction, delayed type hypersensitivity (DTH), Rosette forming cell and macrophage activity. Biochemical items were measured by serum protein and serum albumin. The weight of spleen, thymus and liver were measured. The rancid perilla oil diets decreased humoral and cellular immune responses, the number of peripheral circulating white blood cells and total protein and serum albumin. These results showed that the high rancid perilla oil diet decreased more humoral and cellular immune response, the number of peripheral circulating white blood cells, and total protein and serum albumin than the low rancid perilla oil diet did.