The purpose of this study was to evaluate the effect of Samsoeum(SSE) on cytokine regulation of mouse T cells. The proliferation of mouse CD4 T cells under the influence of SSE extract was measured. When mouse CD4 T cell were stimulated with anti-CD3 and anti-CD28 in various concentrations of SSE extract, it increased proliferation of CD4 cells by 30% in $50{mu}g/m{ell}$ concentration. The proliferation of CD4 cells increased in $100{mu}g/m{ell}$ and $200{mu}g/m{ell}$. Treatment of CD4+ T cells stimulated by anti-CD3e and anti-CD28 with SSE resulted in reduction of $IFN-{gamma}$ and IL-4 levels. SSE has dose-dependent inhibitory effect on $IFN-{gamma}$ and decreased IL-4 by 70% at 50, $200{mu}g/m{ell}$. Oral administration of SSE resulted in increase of CD8+ T cell population in Balb/c mice by 8%. CD4+ T cells under Th1/Th2 polarizing conditions for 3 days with SSE resulted in decrease of $IFN-{gamma}$ level in Th1 cells by 44% and increase of IL-4 level in Th2 cells by 60%. Experimental results of this study show that SSE induces mouse T-cell to transform into Th2, and increases T-cell population and activation.