Persistence of butachlor in clay soil was investigated under field conditions and its residues were determined in soil, rice grain and straw samples. Butachlor was applied at 1.0 kg/ha in rice field. Soil samples were collected at 1, 15, 30, 60, 90 and 120 days after butachlor application and were analyzed for residues. Rice grains and straw were sampled at harvest. HPLC was used to detect butachlor residues. The residue level of butachlor in soil was found 2.56 μg/g a day after butachlor application, which decreased to 0.0028 μg/g at harvest, respectively. However rice grains and straw samples contained 0.003 μg/g and 0.067 μg/g residues, respectively. Half-life of butachlor in the soil was found to be 12.75 days.