Microbiological threat from buildings and rooms and its influence on human health (sick building syndrome)-Poland Ochmanski W, Barabasz W. I Katedra i Klinika Chorob Wewnetrznych Collegium Medicum, Uniwersytetu Jagiellonskiego w Krakowie. In buildings we can observe many different strains of bacteria, over 400 species of mould fungi, many strains of fungus causing the rotting of wood and wood like materials, many species of algae, aphids, and other types of growths and seed plants and also over 30 types of mites especially those seen in house dust. Buildings, especially their interiors have a very specific microclimate. Within it areas of so called ecological lows are formed in which conditions for settlement, growth and reproduction of these organisms take place. A building, which is a hazard to the health of its residents, is called a "sick building" from the term "sick building syndrome". The incidence and development of some types of mould fungus is associated with the production of very toxic metabolites which are called secondary metabolites i.e. mycotoxins. Long term human, especially in relation to children, contact with the species producing the most potent mycotoxins like aflatoxin--Apergillus flavus, ochratoxins--Aspergillus ochraceus, rubratoxins--Penicillium rubrum or strachybotrytoxins--Strachybotrys chartarum may even be the cause of death. Mould fungus or just mould is a saprophytic fungus derived from many different systemic groups (Mucor, Aspergillus, Penicillium, Fusarinum). Fungi can produce lethal mycotoxins such as: alternariol, aflatoxins, gliotoxins, ochratoxins, nivalenol, cytinine, dicumarol, rugulosine, trichoviridine and about 200 more which considering their mutagenicity are potentially dangerous to humans, animals, flora and microorganisms. Research which was begun by Prof. Julian Aleksandrowicz and Prof. Boleslaw Smyk in 1970 and 1971 showed that the so called "leukaemia houses" of leukaemia victims had an abundance of toxinogenic fungus in them, particularly the most potent fungus which turned out to be Aspergillus flavus. Toxinogenic funguses are abundant in many living spaces and cellars in older and also in new housing. Mycotoxins have been shown to be very toxic and harmful and it is no wonder that many inhabitants of these living spaces are constantly ill, mainly upper respiratory tract infections, lethargy, constant headaches, nausea and a general ill feeling. Inhabiting these living spaces for a considerable period may lead to cancer.