Epidemiologic studies of miners have established a causal association between radon exposure and development of lung cancer. During the past decade the focus of attention has turned to the potential risks from exposure to radon in indoor air. Governmental involvement thus far has primarily been aimed at gathering further data and issuing voluntary guidelines for radon control in the indoor environment. The federal government's most recent risk assessment for exposure to indoor radon published in 1992 concluded that exposure to indoor radon results in 13,600 radon-induced lung cancer deaths in the United States each year. As public awareness of such environmental issues continues to grow, physicians will be faced with the need to respond to inquiries regarding potential health effects. Man-made vitreous fibers are silicate glass that have a noncrystalline structure. They have been in production for more than 100 years and are used in numerous applications in residential and commercial settings. The health risks from man-made vitreous fibers that are used in residential and commercial settings are limited to skin and occasional respiratory tract irritation under circumstances of improper installation or maintenance. When glass fiber contaminates an indoor environment, proper repair measures and thorough cleaning of the indoor environment will lead to resolution of any resultant irritant symptoms.