Objective: This paper examines the possible toxicity to immune system in farmers chronically exposed to pesticides. Methods : We compared 43 male farmers exposed to pesticides with 29 male residents who had neither past nor current pesticides exposure. The selected variables for studying immunotoxicity were WBC, CD3, CD4, CD8, CD19, CD56, IgG, IgA, IgM, and IL-2. As part of the baseline questionnaires for the immunotoxicity, subjects were asked about kinds of farming, posticides exposure and medical history. Results : None of the variables for studying immunotoxicity showed statistically significant difference between the two groups. Although the results were not statistically significant, CD4 and the CD4/CD8 ratio decreased and CD8 increased. These effects showed a dose response change with exposure level. In the exposed group, the values of CD3, CD4, CD4/CD8 and CD19 decreased and those of the CD8 and CD56 increased compared to the non-exposed group. Also there was higher prevalence of self-reported disease in the exposed group compared to the non-exposed group. Conclusions: Although statistically significant differences in indices of immunotoxicity in farmers exposed to pesticides were not shown, the results suggest that pesticides may decrease immune function. More advanced test methods for immunotoxicity need to be developed and tested in larger population to detect immunotoxic effects of pesticides.