In order to study the relationship of p53 gene mutation with the occurrence and prognosis of cancer of small intestine, expression of p53 protein was immunohistochemically examined. The results showed that p53 protein expression was high in 75% of small intestine cancer, and positive in 21.1% of the tissues close to cancer. In 7 cases of small intestinal adenoma, only one was immunoreactive. Sixteen samples of normal tissue of the intestine didn't show expression of I}53 protein. The study also found that the degree of p53 protein expression was significantly correlated with that of tumor cell differentiation, invasion, metastasis and prognosis.