The report gives results of a characterization of multimedia emissions from 39 source categories of conventional stationary combustion systems. In the assessment, existing emissions data were first examined to determine the adequacy of the data base. This was followed by a measurement program to fill identified data gaps. Emissions data obtained from the sampling and analysis program were combined with existing emissions data to provide estimates of emission levels, and to define the need for additional data. Study results indicate that flue gas emissions of NOx, SO2, and particulate matter from the 39 source categories account for approximately 86, 66, and 36%, respectively, of the emissions of these pollutants from all stationary sources. Additionally, flue gas emissions of sulfates and several trace elements from coal- and oil-fired combustion sources also require further attention. POM compounds in flue gas emissions are mostly naphthalene, phenanthrene, and pyrene. However, dibenz(a,h)anthracene and possible benzo(a)pyrene, both active carcinogens, were detected at a limited number of coal- and wood-fired sites. Concentrations of iron, magnesium, nickel, and phosphorus in waste-water streams are at levels that may be of environmental concern. Data on coal fly ash and bottom ash show 11-16 trace elements at potentially harmful levels.