A facile, rapid and sensitive spectrophotometric method was developed for the determination of fenitrothion in its formulations, water, food grain and agriculture soil samples with newly synthesised reagent. The method was based on the alkaline hydrolysis of fenitrothion pesticide and resultant hydrolysed product of fenitrothion was coupled with diazotised 4,4'-methylene-bis-(p-amino-3'-hydroxybenzanilide) in basic medium to give orange coloured product having lambda(max) 480 nm. The formation of coloured derivatives with the coupling agent is instantaneous and stable for 48 h. Beer's law was obeyed in the concentration range of 0. 1-19.0 mu g ml(-1). The proposed method is sensitive, easy to operate and permitted the determination of fenitrothion with a detection limits of 0.085 mu g ml(-1). The experimental results indicate that the procedure can eliminate the fundamental interferences caused by other pesticides and non-target ions, which made these methods more sensitive and selective. The method was applicable to the determination of fenitrothion residue in water, food grain and soil samples up to ng level. (C) 2006 Elsevier B.V. All rights reserved.