This testimony concerned the activities of NIOSH and the Center for Environmental Health (CEH) of the Centers for Disease Control concerning indoor air quality. Since 1971 NIOSH has conducted over 200 indoor air quality investigations. More than 90 percent of these were conducted in the last 5 years. Nearly all were conducted in response to worker symptoms or illnesses which were thought to be related to the building environment in which the people were working. Generally, the indoor air pollution evaluations conducted were categorized by the source of contamination in the environment, if identified, or otherwise by the type of symptoms or illnesses experienced by the workers. These categories of contamination include contamination from outside the building, from building materials, from copying machines, hypersensitivity pneumonitis, from chemicals used in building maintenance, and inadequate ventilation. Often the results of investigations are hard to interpret due to the highly emotional nature of many of the situations involved. While more serious illnesses occasionally have been attributed to working in these building environments, no clear evidence of health problems more serious than apparent allergic reactions in a few individuals to specific office contaminants has been found. The CEH conducted a survey of State health department programs for hazard evaluations of nonoccupational indoor air pollution.