The simultaneous acquisition of both positive ion and negative ion data under chemical ionization mass spectrometric conditions can aid in the confirmation of assignments made by electron impact gas chromatography mass spectrometry or electron capture gas chromatography. Pulsed positive ion negative ion chemical ionization mass spectrometry coupled with fused-silica capillary column gas chromatographic methods is shown to be useful in environmental and hazardous waste sample analysis. The chemical ionization conditions which maximize sensitivity and the amount of molecular ion information for the priority pollutants are presented. Replicates of response factors for these compounds show good precision. Saturation is observed about 10 micrograms for those pesticides which give linear responses from 50 picograms to 1-10 micrograms.