The disposal of wastes from energy production, particularly solid wastes from coal conversion processes, requires a thorough understanding of both the waste and the environment. Environmentally responsible disposal requires an appreciation and understanding of all of the complex interactions that can occur between the waste and the environment. Additionally, the importance of site characterization cannot be overemphasized, since local geology plays such an important part in the transport and fate of potentially problematic trace elements and other contaminants. Waste characterization techniques must be scientifically valid, comprehensive, and thorough. The focus of this paper is on the importance of the selection and application of scientifically valid methods for characterizing wastes. Selection criteria for scientifically valid evaluation techniques for the characterization of coal conversion solid waste are discussed, and guidelines for selection are provided. The importance of understanding all possible environmental consequences must be considered, including water-to-waste and waste-to-waste interactions, as well as leachate-to-sediment interactions. The importance of the philosophical integration of all aspects of disposal, site characterization, and waste characterization are discussed. The application of scientifically invalid characterization methods or incomplete site characterization is poor science at best and can lead to false conclusions.