Fifty Australian buildings of five different types (earth-covered, earth-sheltered, earth-walled, those ‘dug out’ of self supporting rock, and above-ground dwellings), are currently being surveyed for radon activity. Using nuclear track detectors over a one-year period, 14 of these sites so far returned have yielded a highest level of 388 Bq m-3 (interior air, earth-wall house) and a lowest level of 19 Bq m-3 (standard above-ground cavity-brick house).