This report describes the results obtained and data analysis from an interlaboratory evaluation of EPA Method 608 (Organochlorine Pesticides and PCBs). The method is designed to analyze for 16 single-compound pesticides, chlordane, toxaphene, and seven Aroclor formulations in water and wastewater. All were included in this study except endrin aldehyde, sufficient quantities of which could not be obtained. The study design required the analyst to dose six waters with eight analytical groups, each at six levels. The six dosing levels of each substance or combination represented three Youden pairs, one each at a low, an intermediate, and a high level. The six waters used were a laboratory pure water, a finished drinking water, and a surface water, all collected by the participant, and three low-background industrial effluents (SICs 2869 and 2621). A total of 22 laboratories participated in the study. The method is assessed quantitatively with respect to the accuracy and precision that can be expected. In addition, results of method detection limit studies are included as are qualitative assessments of the method based upon comments by the participating laboratories.