This testimony before the Subcommittee on Health and the Environment discussed the sulfur oxides problem and the roles of the workers at NIOSH in completing epidemiologic studies intended for incorporation into the 1972 revision of the "EPA Air Quality Criteria Sulfur Oxides." Instead the work appeared as a monograph entitled "Health Consequences of Sulfur Oxides: A Report from CHESS, 1970-1971" and was attacked in the press. Dr. Finklea defended the roles of both himself and his investigative team in their efforts to obtain the information requested in the time allowed, citing the complexities of the task of determining the health effects of ambient air pollution. Three approaches have been taken to gather such information: use of experimental animals in the laboratory, intensive study of a few patients or volunteers in a clinical lab setting, and epidemiologic or community studies involving groups of people. A number of the factors in the efforts made were less than optimal including a lack of qualified professionals, the need for various technical disciplines to interact in noncustomary ways, the lack of sufficient time, the unavailability of needed techniques, the inabilities of available clinical air monitoring and statistical techniques, the limited funds and personnel available, and the restriction of the studies to persons living close to an air monitoring station. Even with these limitations, Dr. Finklea states his belief that the monograph as published was technically sound and that appropriate caveats were included.