A study on the leaching of chlorpyrifos in an oil palm agro ecosystem was conducted in an oil palm plantation in Sepang, Selangor. The insecticide chlorpyrifos was sprayed using a knapsack sprayer at the recommended and double the recommended dosage. Soil samples were collected at different depths, viz. 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm at the following inter vals: -1 day (before treatment), 0 day (day of treatment, 6 hr later), 1 day, 3, 7, 14, 30 and 60 days after treatment. Recovery of chlorpyrifos from the soil spiked with chlorpyrifos at 4-50 μg kg^-1 ranged from 88%-99% with the coefficients of variation r anging from 2.0% to 7.5%. Chlorpyrifos residue was detected at 0-10 cm and 10-20 cm depths when applied at the recommended and double the recommended dosages, respectively. The residue was only detected in the soil for up to five and seven days after treatment, respectively, when applied at the recommended and double the recommended dosages.