Right behind cardiovascular diseases, cancer ranks second in causes of death in Austria. It can develop in any human tissue, is characterized by an abnormal cell growth and follows a multistage development which can be divided into three steps - initiation, promotion, progression. Healthy cells are in homoestatic balance between cell division, differentiation, and apoptosis. During cancer development, this balance is shifted towards proliferation, dedifferentiation and inhibition of apoptosis. Substance testing has to be conducted according to the 3 R - concept. According to the OECD - guideline 451, substances have to be examined for genotoxicity and their cell - transforming potential properties with in vitro methods. Substances of which more than 1000 tons per year are produced have to be tested additionally with an in vivo test. For in vivo testing, a two year bio assay on rodents has to be conducted. This test system is expensive, time consuming, and the ethic issues have to be registered. Mucil Air TM is a cell culture model which we have tested for its potential to be established as an alternative test method for the two year bioassay on rodents.