Mancozeb, a polymeric complex of zinc and manganese salts of ethylene bisthiocarbamate (EBDC), is used widely in agriculture as fungicides, insecticides, and herbicides. Mancozeb can be occupationally and environmentally exposed to human and has been reported to induce estrogenic activity, therein it is considered as an endocrine disrupter, We investigated the effects of acute exposure of Mancozeb on the immune function in mice. After single oral administration of Mancozeb to female ICR mice, the immunopathological parameters (body- and organ-weight, splenic cellularity hematological parameters), mitogen (Con A, PHA+IL-2, LPS)-induced splenocyte proliferation (SP) and splenic IgM plaque forming cell (PFC). WBC and splenic cellularity were decreased, but liver-, kidney-, and spleen-weight were increased when compared with control group. Splenic IgM PFC against SRBC was slightly lowered. Mitogen-induced proliferation of spleen cells from Mancozeb-treated mice was not signifcantly changed ex vivo, however, SP in vitro were significantly lowered in concentration dependent manner. These results indicate that Mancozeb could affect the immune function in mice.