In this cross-sectional study, the authors examined the relationship between an unusual combination of indoor air contaminants in a school and adverse health effects among the attending children. A leaking roof and damp floors, together with gaseous leaks from the sewage system, led to a combined exposure of hydrocarbons, 2-ethylhexanol from plastic floor coverings, and moisture-associated microbes. The health status of 274 children in the school was assessed via repeated symptom questionnaires. Statistical analysis revealed a relationship between the indoor air contaminants and adverse health outcomes such as respiratory irritation, asthmatic symptoms, eye and general symptoms, and increased occurrence of common viral respiratory infections. No association was found between the exposures and doctor-diagnosed asthma, other allergic diseases, or bacterial respiratory infections. Chemical contaminants from the sewer system and damp construction materials were identified as the source of the problem. Remediation of the school building improved the indoor air quality and the health status of the children.