Building related illnesses are a common problem in developed countries and are expected to increase rapidly in urban India. Although objective physical abnormalities are not generally found except in a few specific diseases like Legionnaires' disease, the symptoms can be uncomfortable and even disabling. In this review we initially introduce the concept of indoor air pollution and building related illnesses. Subsequently we review the sources of and exposure to the pollutants along with their health effects and the approach to a patient of suspected building related illness. We conclude by discussing the measures for the control of indoor air pollution.