A bacterium designated Tr A and capable of decomposing trifluralin in the presence of glutamate, lactate, acetate and yeast extract was isolated. Optimum pH for growth of this organism was 6.5 in a glutamate medium containing 0.01% trifluralin. Maximum decomposition of the herbicide occurred at pH 7.4 A threshold concentration of 0.05% trifluralin was necessary for the growth of this organism. Ninety-five per cent of the trifluralin was decomposed within 21 days in an 0.01% trifluralin medium, but none was degraded at a concentration of 0.05%. The herbicide remained stable for 10 days in an aqueous solution at different pH levels.