Distribution and persistence of fenitrothion in rats were studied following oral administration of a single dose 300 mg/kg of body weight. Residue of the parent compound was analyzed in blood, liver, kidney, brain, lung and heart 2, 4, 6, 8 hours and 1, 2, 3, 5, 7 days after oral administration. The maximum concentration of fenitrothion appeared in the blood, kidney, heart on the 2 hour and liver, brain, lung on the 4 hour. Residues of the parent compound in kidney were much higher and persistent than other tissues and the pesticide was not detected on the 7th day. Recoveries were ranged from 83.0(lung, $1 mu g/g$) to 97.5%(blood, $1.5 mu g/ml$).