The objectives of the National Incinerator Testing and Evaluation Program (NITEP) were to define optimal design and operating characteristics for different types of municipal solid waste (MSW) incinerators, relate the defined operations to atmospheric emissions, identify the best options to control emissions, and develop guidelines for the operation of MSW incinerators and for emissions. This report provides a summary of the facilities tested under the NITEP ash characterization program, the experimental approach used to evaluate the residues, and the type of data generated. The data have been compiled and presented to illustrate significant trends and to show how these trends relate to the guidelines for ash management. The feasibility of using solidification as an acceptable treatment technique for these residues is also presented.