Dehydroepiandrosterone (DHEA), the most plentiful steroid hormone, has been convincingly known to have many biological effects and diverse influence in various types of cells, tissues and organs. The effects of DHEA on the humoral and cellular immune response are widely tested, but it is unclear whether DHEA itself serves as an activator of immune function and the literature pertaining to the in vitro effects of DHEA remains contested. In the present paper, the effects of DHEA on the thymocytes in vitro were studied. The results showed that DHEA could enhance the expression of Fas and Fas-L and induce thymocyte apoptosis. This suggests that dehydroepiandrosterone may induce the apoptosis of thymocyte through Fas/Fas-L pathway.