Organophosphorus pesticides (OPPs) were determined in matrices of animal origin by dual column capillary gas chromatography using nitrogen-phosphorus detection (NPD). This method was tested on cow milk and on liver and muscle of wild boar. The isolation of these pesticides was performed by liquid partition followed by cleanup with solid phase cartridge (SPE C18), after extraction from the matrix. The analytes identification was obtained by comparing the retention times in two columns with different polarity. The quantification of each OPP was obtained using parathion-ethyl as internal standard. The method was developed in a UNI EN ISO 9001:2000 certified laboratory. The recovery, investigated by analyzing samples spiked at 5, 10 and 50 ppb, ranged from 59 to 117% in milk, from 60 to 81% in liver and from 68 to 76% in muscle. The limit of quantification (LOQ) and limit of detection (LOD) were, respectively, 5 and 1 ppb for each compound and allowed quantifying the residues below the legal limits.