of tea on cancer by immune regulation. Methods　A tumor model was induced in mice using carcinogen, 4-methyl-nitrosoamino-1-(3-pyridyl)-1-butanone (NNK), to examine their changes in immune function and the effects of green tea, mixed tea and polyphenol on protection from tumor. Results　During the four weeks of observation after injection of NNK into mice, their immunological indicators, such as cytophagocytosis of macrophage in the abdominal cavity, chemiluminescence of peripheral leukocyte, delayed allergic reaction, count of antibody-forming spleen cells and activity of spleen nature killer cells, etc. increased or decreased to various extent, as compared with those in normal controls. It was found that whether green tea, mixed tea or polyphenol all showed significant protection from adverse changes in immune functions. Conclusion　Tea and its components had signi