The authors discuss problems associated with indoor atmospheric pollution including a large number of pollutants coming partly from outdoors and produced partly by internal sources. Passive tobacco smoke, radon decay products, carbon monoxide, nitrogen dioxide, formaldehyde, asbestos fibers, microorganisms and allergens are the most important contaminants. Health risks associated with indoor air pollution require an overall strategy to control sources, dilute indoor contaminants and promulgate specific regulations.