A study was conducted in cow raw milk to measure residues of 15 organophosphorus pesticides, used as dairy cattle ectoparasiticides or in crops used for animal feed. The determination was carried out improving a previous method by dual column capillary gas chromatography with nitrogen-phosphorus detection (NPD). The samples, collected in 9 Italian dairy plants directly from the tank trucks during the delivering, were representative of 3,974 tonnes of raw milk. Approximately 4.4 % of the 298 samples analyzed contained residues, always in traces. The main pollutant was chlorpyriphos. These data were compared with a previous similar investigation