The document "Test Methods for Evaluating Solid Waste," Office of Solid Waste, Manual SW-846, provides a compilation of methods for evaluating RCRA solid wastes for environmental and human hazards. One of the methods in this document, Method 8000, provides guidance on gas chromatographic analysis with specific details on instrument calibration, maintenance, and quality control. Since most of the GC methods in the SW-846 manual specify the use of packed columns, and since for the past 10 years the scientific community has had access to the fused-silica capillary column technology, we were asked by the U.S. Environmental Protection Agency to develop gas chromatographic procedures that employ fused-silica open-tubular columns. When compared to packed columns, the open-tubular columns offer improved resolution, and thus better selectivity, increased sensitivity, and shorter analysis times. Furthermore, when injection is performed using an injection tee and two dissimilar columns connected to two identical detectors, then sample throughput is increased by a factor of two because the primary and confirmatory analyses are being conducted simultaneously. We have used the dual-column/dual-detector approach in this study to establish gas chromatographic conditions for six groups of target analytes: Method 8040 phenols, Methods 8080/8081 organochlorine pesticides, Method 8090 nitroaromatic compounds, Method 8110 haloethers, Method 8120 chlorinated hydrocarbons, and Methods 8140/8141 organophosphorus pesticides. In each case, the list of target analytes was expanded to cover more target analytes than those currently listed in the methods mentioned above. The approach taken was as follows: select columns for the dual column/dual-detector approach, establish conditions that give the best chromatography for the target analytes in terms of resolution and peak shape, establish method reproducibility and linearity, select at least one internal standard and surrogate compound per method, and finally test the procedure with blind performance evaluation samples of known composition as well as with extracts of real matrices.