OBJECTIVE To investigate the inhibitory effect of dehydroepaimdrosterone (DHEA) on the growth of transplanted Morris hepatomas (7288CTC) in vivo in rats. METHODS 21 Buffalo rats were randomly devided into 4 groups, including one blank control group (n = 5), one group for tumor-bearing control (n = 6), and 2 experimental groups with DHEA (n = 6) or DHEA-s (n = 4). DHEA or DHEA-s was fed to the rats for 4 weeks immediately after Morris hepatomas (7288CTC) was implanted in both flanks. Phenotypes of the spleen lymphocytes were examined by flow cytometry, Akt and PTEN expression in tumor cells was detected by Western blot and immunohistochemistry. RESULTS Tumor weights of DHEA treated group were less than those of the control (P less than 0.05), the inhibitory rate was 43%. The results of Western blot and immunohistochemistry showed that in DHEA tumor group,the expression of phosphorilated Akt protein was decreased, the expression of PTEN was enhanced, the percentage of CD3 positive cells and the ratio of CD4/CD8 were increased (P less than 0.05). CONCLUSIONS DHEA can inhibit tumor growth, possibly via the inhibition of the Akt signaling pathway as well as modulating the immune function.