Extensive field testing and modeling was conducted at the ALCOSAN Wastewater Treatment Plant (WWTP) during the spring and summer of 1994 to determine the levels of odors, volatile organic compounds (VOCs), and hazardous air pollutants (HAPs) emitted to the atmosphere. VOCs and HAPs are regulated by Title I and Title III, respectively, of the 1990 Clean Air Act Amendments (CAAA). The Bay Area Sewage Toxics Emissions (BASTE) model was used for estimating HAP emissions, and Joint Emission Inventory Program (JEIP) factors were used for estimating VOC emissions. The results of the emissions inventory program demonstrated that the ALCOSAN WWTP is not a major emitter of VOCs or HAPs as defined by the CAAA. Earlier estimates, using more conservative U.S. Environmental Protection Agency (EPA) emission factors, had shown VOC emissions significantly above the Title I major source limits of 50 tons per year for Pittsburgh, Pa.. Because ALCOSAN is not a major emitter of VOCs, conventional odor-treatment technologies, such as wet scrubbing, can be used at ALCOSAN instead of more sophisticated VOC-treatment technologies, such as thermal oxidation.