The adsorptive stripping differential pulse voltammetric method was proposed for the determination of fenitrothion [O,O-dimethyl O-(4-nitro-m-tolyl)phosphorothioate]. The voltammetric response was evaluated in 0,04 mol ^-1 Britton-Robinson buffer with respect to the accumulation time and potential, and concentration dependence. The relationship between peak current and fenitrothion concentration was linear within the range of 1x10^-8 – 1x10^-6 mol l^-1. In spiked water the detection limit of fenitrothion, estimated from 3 times the standard deviation, was 36 ng l^-1. Interference from some other organophosphorus insecticides on the determination of fenitrothion were studied.