The research program of the National Environmental Research Center in Cincinnati, Ohio, is directed toward solving major environmental problems in wastewater management and treatment, drinking water, solid wastes, toxicants from automobile exhaust and other sources, industrial and hazardous waste management and control, radioactivity emissions from nuclear power plants, and methods development and quality assurance. In this, the Second Annual Report of the National Environmental Research Center, the programs are described and progress during 1973 is delineated. Articles on various specific projects provide some detailed results of research progress.