Abstract: To inv est igate the expression of ras and c-erbB-2 in skin cancer induced by arsenic.By means of immunohistochemical technique using mono clonal antibodies to ras and c-erbB-2 oncoproteins in 10 cases of skin cancer induced by arsenic.The positiv e rate for overexpression of ras and c-erbB-2 oncoproteins in skin cancer induced by arsenic were 90% (9/10)and hig her than those of the reported.The positive position for overexpression of c-erbB-2 and ras were mainly observed on cell memberance and cytoplasm of epithelial cells,respectively.It is sugg ested that the oncogene may play a role in carcinogenic mechanism of arsenic.