The Austrian radon mitigation joint research project SARAH (supported by the Austrian Ministry ofEconomy and the Government of Upper Austria), a two-year follow up study of the Austrian NationalRadon Project (NRAP), was started in 1996. Objectives of the research project were to find simple,cost effective experimental methods for the characterisation of the radon situation in dwellings and toevaluate technically and economically the implementation of state of the art remedial actions forAustrian house types. After an intercomparison exercise of the assigned radon measuring instrumentsand detectors five houses were closely examined in regions with elevated radon levels in the federalstate of Upper Austria. In this research work for the first time an extended Blower-Door method(which is conventionally used for determining the tightness of buildings) was successfully applied toradon diagnosis of buildings.In this paper the methods used for the radon diagnosis, the applied mitigation measures and the relatedtechnical and economical aspects are discussed. In conclusion of the results of this project a commonstrategy for solving the radon problem in Austria in the future is presented briefly.