Abstract In October 1992 a national news program aired a segment that discussed health effects associated with the indoor, nonindustrial environment. As a direct result of this program, by February 1993 the National Institute for Occupational Safety and Health health hazard evaluations program received approximately 500 requests to evaluate health and environmental problems in offices, schools, and other non-industrial work settings related to the indoor environment. Of the 160 work sites selected for a site visit, 105 were office buildings. In 80 of these, the investigation followed a prescribed protocol for both symptoms and environmental data collection in a study area within each building. Using a standardized, self-administered questionnaire, symptom prevalences of 18 symptoms and 4 symptom groups were calculated using three different definitions: (1) on the day of the evaluation; (2) at least once a week during the preceding 4 weeks; and (3) at least once a week during the preceding 4 weeks, and having the symptom improve when the employee left the workplace. Prevalences of the most commonly reported symptoms, using the latter definition, were: tired or strained eyes (33%); dry, itching, or irritated eyes (30%); unusual tiredness, fatigue, or drowsiness (26%); headache (25%); tension, irritability, or nervousness (23%); and stuffy or runny nose, or sinus congestion (22%). All 18 symptoms were more likely to be reported by females, and 40 percent of female respondents reported experiencing at least one upper respiratory symptom (sore or dry throat, stuffy/runny nose or sinus congestion, or sneezing) at least once a week that improved when they left work. Limitations of the study include the nonrandom selection of buildings and the self- selection of the evaluated areas within buildings by the health hazard evaluation requestor.