A method for monitoring pesticides in apple samples, including Soxhlet extraction, an evaporation step and capillary gas chromatography with nitrogen-phosphorus detection, is applied to a decay study of the carbamate pesticide ethiofencarb. The evaporation step is carried out by a surface nitrogen flow and the recoveries of ethiofencarb measured in standard solutions of ethyl acetate and apple extracts. The results of the decay studies show that ethiofencarb is degraded in the apple peel faster than in the interior of the fruit. The methodology is then applied to decay studies in the laboratory of the organophosphorus pesticides, diclofluanid, fenitrothion and malathion.