This study was conducted on 80 subjects in one of the major companies formulating pesticides in Egypt. All subjects were males. Workers in the production sectors were 55 subjects, their age ranged between 26-55 years (mean SD) (44.26 5.33), they were exposed to different types of organophosphates and carbamates insecticides and pesticides for agricultural production. All of them work 8 hours /day with over time and they did not use any protective equipment during work hours. 25 adult men without occupational exposure to pesticides were chosen as control group from other departments of the company, their age, sex and socio-economic standard were matched with the exposed group. Our aim is to illustrate the effects of occupational exposure to pesticides on human cell mediated immunity and to assess this relation with the prevalence of viral hepatitis (HBV&HCV) among the workers. Investigations done for the examined group were Hb, WBCs, Lymphocytes, sALT, HbsAg, Anti HCV, CD4,CD8,CD4/CD8,CD56,IL-2, and abdominal ultrasonography. The most significant results were alteration of the cell mediated immunity among the exposed group and increase the prevalence of Hepatitis B virus (HBV) and Hepatitis C virus (HCV) among the exposed group which is confirmed by their effects on the liver which is diagnosed by abdominal ultra-sonography. This study illustrated the relation between different liver diseases as bilharzia liver, liver cirrhosis and mixed liver disease and cell mediated immunity.