Chitosan is derived from chitin by a process of controlled deacetylation. In the present study, we investigated the effects of chitosan on the production of cytokines such as interleukin-2 (IL-2), interferon-$gamma$ (IFN-$gamma$), interleukin-4 (IL-4), and interleukin-10 (IL-10) in mice. The culture supernatants of splenocytes exposed with chitosan alone or chitosan plus cell stimulants, lipopolysaccharide (LPS), concanavalin A (Con A), and phytohemagglutinin-P (PHA-P) were harvested to assay IL-2, IFN-$gamma$, IL-4, and IL-10 production. IL-2, IFN-$gamma$, and IL-4 from splenocytes exposed to chitosan showed a greater increase compared to the PBS control group. IL-2 and IFN-$gamma$ levels in the culture supernatants from splenocytes exposed to LPS+chitosan were higher than those of the groups exposed to LPS alone. IL-4 and IL-10 levels in the culture supernatants from splenocytes exposed to LPS+chitosan were lower than those of the groups exposed to LPS only. These findings demonstrate that chitosan upregulates the immune responses by Th1 cytokines (IL-2 and IFN-$gamma$) and downregulates those by Th2 cytokines (IL-4 and IL-10) in LPS-associated immunity. These results show the potential of its usefulness for balancing the Th1/Th2 immune response, if more research results were accumulated.