Background:  Plant essential oils play prominent roles as flavoring agents in the food industry and as fragrances for the perfume industry. The World Health Organization has recommended that traditional plants used for the treatment of diseases need further scientific investigation on their toxic side effects. Objectives: The current study was conducted to evaluate the histopathological effect of three plants' essential oils that could be used as insecticides.  Methods: Thirty adult male albino mice were divided into five groups. Group I was considered as a control group. Group II, III and IV received cinnamic aldehyde, benzyl alcohol and eugenol essential oils respectively.  For comparison with the tested essential oils, Group V received the organophosphorus insecticide dimethoate. Results: Histological examination of liver and renal cortex of animals received the essential oil cinnamic aldehyde or benzyl alcohol revealed a nearly normal histological structure of hepatic parenchyma by Hematoxylin and eosin stain, and normal collagen distribution demonstrated by Gomori's Trichrome stain.  Examination of the group IV treated with eugenol revealed few focal areas of degeneration in hepatic parenchyma and in some renal tubules.  On the contrary, mice treated with dimethoate manifested severe affection of the hepatic parenchyma with characteristic hepatic zonation and many degenerated cells, pyknotic nuclei and vacuolated cytoplasm in addition to intense cellular infiltration.  Thyrodization of the renal cortex of dimethoate treated mice was consistent finding in most of the examined specimens.  Many convoluted tubules appeared irregular dilated with flattened epithelial lining.  Their lumina were occupied by cellular casts and hyaline material. Thickened basement membranes of the renal tubules with disrupted brush border were also observed. Moreover, extensive fibrosis of hepatic parenchyma and renal interstitium were detected in this group treated with dimethoate. Conclusion: the tested essential oils did not demonstrate significant adverse effects on the liver and renal cortex of albino male mice, while the organophosphorus insecticide, dimethoate, had significant hepatotoxic and nephrotoxic effects.  Further studies are needed that include more animals and to address other factors such as gender differences, time course, dose response, blood chemistry, and other biochemical targets prior to any recommendation for the usage of any of these chemicals as insecticides.