Nitrogen becomes a significant solid waste parameter when it is evaluated in conjunction with two other parameters, namely carbon and hydrogen. The change in the C/N ratio of compost can be used to determine (1) the degree and rate of biological decomposition of organic matter in the compost, and (2) the suitability of the final product for use in agricultural soils. A knowledge of the nitrogen, carbon, and hydrogen contents of an incinerator's load and combustion products can also enable the engineer and scientist to (1) calculate the theoretical air requirements and combustion products, (2) formulate appropriate material and energy balance equations, and (3) evaluate and control effectively the efficiency of an incinerator system. To ensure the precise and accurate determination of the nitrogen content of solid wastes, investigations of the applicability of existing analytical procedures were conducted in this laboratory. Analyses of solid waste samples, containing up to 8 percent nitrogen, have demonstrated that the Kjeldahl-Wilfarth-Gunning-Winkler Method, the Comprehensive Nitrogen Method, and the Automated Dumas Method (as employed in the Coleman Nitrogen Analyzer) may be employed in the characterization of solid wastes. Detailed descriptions of these three methods are presented.