Immunomodulating and anti-tumor activities of orally administered Chai-Ling-Tang (Japanese name: sairei-to, ST) were investigated. The oral administration of ST into mice augmented the antibody response to intraperitoneally administered 2, 4, 6-trinitrophenyl-haptenated sheep red blood cells (TNP-SRBC). Orally administered ST showed also an enhancing effect on the antibody response to TNP-SRBC administered by the oral route. In addition, orally administered ST markedly activated the peritoneal macrophages to enhanced phagocytic and lysosomal enzyme activities. A significant inhibition of tumor growth was observed in a syngeneic tumor-mouse system when ST was administered orally. These results suggest that ST has an efficiency as an oral adjuvant or an oral biological response modifier (BRM).