We have studied 108 cases of brain tumors by immunohistochemical staining utilizing an antiserum against the src gene product and GFA protein in order to elucidate the relationship between the brain tumors and the transforming genes. While the normal human brain tissues were not positive with the antiserum against the src gene product, several astrocytomas were clearly positive and other brain tumors were negative with the same. Src-gene product related peptide was detected in some of the human astrocytomas.