A GC-MS study was carried out to identify the decay products of methyl parathion in water, soil and rooted vegetable (radish) at different time intervals. The water (pH 5.5 and 8.0), soil (pH 7.5) and radish samples collected after the first half life shows the presence of O,O dimethyl O-p-nitro-2 or 3-hydroxyphenyl phosphoorothioate which persists upto the 30th day in the alkaline water and soil samples. However, in acidic water methyl parathion is oxidized to give methylparaoxon.