A multidisciplinary approach to microbiological implications of indoor air is fruitful for research as well as management of health and building problems. The Finnish and the Danish mold programs are examples of such productive collaborative studies. Dust samples taken from classrooms in schools where occupants complain of building-related symptoms (BRS) demonstrated an inflammatory potential in vitro, measured as a release of cytokine interleukin (IL)-8. An increase of the metabolite NO and liberation of tumor necrosis factor (TNF)-a and other cytokines during exposure were obtained in vivo, was presented based on these programs and on epidemiological studies on residential fungal contamination and health conducted in Canada and The Netherlands. New methods for.assessing fungal exposure are PCA analysis for the toxigenic mold Stachybotrys chartarum and EPS-Asp/Pen for detecting of Asperg1llus and Penicillium in dust. Based on a limited data set it is shown that emission rates of fungal spores are inversely proportional to relative humidity (RH), directly related to flow rate and to surface loading. Poor maintenance, risk constructions and risk materials are described in several studies as the main causes of water damage in buildings.