Mass spectrometry/mass spectrometry (MS/MS) has been shown to be useful in the analysis of environmental samples for low (ppt) levels of compounds like polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in cases where interfering materials present in the samples made analysis by high resolution mass spectrometry (HRMS) difficult or impossible. While the technique shows promise because of its high selectivity, researchers have reported stability problems with mass spectrometry/mass spectrometry instruments and other questions regarding the reproducibility of analytical results exist. This study was undertaken to develop an MS/MS method for the analysis of PCDD/Fs, determine the stability of an MS/MS instrument over a period of months and to compare analytical results obtained by MS/MS with those obtained by HRMS. The results demonstrated that by following the protocol developed in the study, an MS/MS instrument can generate reproducible analytical results over a period of months and that quantitative results obtained by MS/MS were not significantly different from those obtained by HRMS.