The purpose of this project was to determine the planned cogeneration development by the utility and industrial sectors; to assess the environmental impacts and energy savings from cogeneration; and, to identify potential environmental issues and regulations impacting cogeneration development. Major emphasis was placed on environmental impacts. The study investigated the energy savings and environmental impacts of five industrial facilities which are considering a switch to in-plant cogeneration. Potential regional environmental impacts of cogeneration development in New England, the Tennessee Valley Authority service area and northern New Jersey were also determined. Finally, the environmental impacts of a cogeneration-based district heating system were considered. It was found that there are a number of factors which determine the relative magnitude of environmental impacts of a cogeneration system compared to a conventional energy supply system.