Hazardous waste incinerators are tightly regulated under the Resource Conservation and Recovery Act (RCRA). On the other hand, processes for which the primary purpose is production of energy but, incidentially, burning hazardous wastes are exempt from the RCRA incineration regulations. EPA is concerned about the impact of this 'Energy Exemption' and has initiated a test program to determine if and to what extent regulation of such processes may be required. The most significant practice that currently is excluded from regulation is disposal of hazardous materials in industrial boilers. There are currently in the U.S. approximately 240,000 operating industrial boilers and a large percentage of these boilers are accessible to hazardous wastes. This paper describes the testing of 12 such industrial boilers of various types using varying waste materials and test 'spiked' materials. Test site selection is discussed, sampling and analytical methodologies are presented and test results are summarized. The primary focus of the test program was on the ability of the boilers to destroy principal organic hazardous compounds (POHCs) and also to characterize and quantify emissions of products of incomplete combustion (PICs). Measurements of particulate emissions, CO, NOx, and THC were also recorded. Attempts were made to establish correlations between boiler type, boiler operating parameters and waste destruction efficiencies.