A variety of analytical procedures have been employed for the determination of the volatile solids in solid wastes. Researchers, such as Kaiser, have adapted the ASTM standard procedure for coal to the analysis of refuse and residue. Other investigators, such as Schoenberger and Wiley and Spillane, have attained more complete oxidations by utilizing open-crucible techniques. A modification of the procedure proposed by the American Public Works Association has been used extensively by the Research Services Laboratory Staff for the characterization of refuse, residue, and fly ash. After the observation of the weight lost by each sample, the percent ash and the percent weight loss on heating at 600 C are calculated. A detailed description of the procedure is presented.