Application of ethoprophos as a nematocide in potato field crop and dosing to rats has been studied. Ethoprophos extraction, followed by quantitation by gas chromatography using flame photometer detector. Results demonstrate that ethoprophos clear from soils at 51 days and from cultivated potato roots at 44 days from nematocide application. Serum biochemical and histopathological studies on laboratory analyses proved that ethoprophos have a drastic effect on liver and kidney functions as well as accumulate ethoprophos residues in liver, followed by kidney and finally muscles. Finally, this work referred to that the determination of pesticide residues in soil and potato is regulatory significance in addition to that ethoprophos nematocide have low environmental persistence, but a high toxicity.