Incineration of mixed waste solvents in two process kilns was investigated during two 1-week field testing programs. The overall objective of the study was to evaluate the effectiveness of the two process kilns in destroying hazardous wastes and quantify stack gas emissions. During the test programs, samples of the hazardous wastes fired in the kilns were collected and analyzed for principal organic hazardous constituents POHCs, selected trace metals, and chlorides. Air emissions were sampled and analyzed for particulate matter (including trace metals); volatile and semivolatile POHCs found in the wastes and other products of incomplete combustion (PICs); and criteria pollutants including sulfur oxides, nitrogen oxides, carbon monoxide, and hydrochloric acid. Test results indicated that destruction and removal efficiencies (DREs) of POHCs at one site failed to meet the 99.99 percent level. POHC DREs at the second site were generally above this level. This disparity of results was attributed to difference in kiln operating temperature.