The term sick building syndrome (SBS) is frequently used to describe a set of symptoms often reported by occupants of certain buildings. The symptoms are supposed to be direct or indirect consequences of an inadequate indoor climate. Typically, a majority of the occupants in these buildings complain, and the most frequent complaint is irritation of eyes, nose, and throat. Many different factors are known to be potential agents for the symptoms and no definitive causality has been identified yet. In consequence authors of publications on indoor air quality have been using the SBS term in different ways. A review of literature indicates that in supposed "sick buildings" only the prevalence of irritation of mucosal membranes and headaches seems to differ significantly from the prevalence in buildings considered to have a normal indoor climate. Volatile organic compounds (VOC) are known to have a potency to cause symptoms like those included in SBS. A dose-response relation for sensory reactions and mucosal irritation caused by volatile organic air pollutants is discussed, and a tentative guideline at 3 mg/m3 (about 0.9 PPM toluene equivalent) for the total volatile organic compounds (TVOC) is suggested for the nonindustrial indoor climates.