Recent studies indicate that radon hazard is a widespread geological hazard. High radon concentrations in houses may cause lung cancer, and indoor radon comes primarily from the geological unit on which houses sit. Taking for example the Reading Prong granitic gneiss belt in the eastetn U. S., the author, while working in the U. S., studied the relationship between nearsurface radon and uranium concentrations as well as the correlation between ground uranium distribution and cancer mortality of residents. The regional uranium distribution was mapped by using airborne gamma-ray spectre-metric data. As a result, the applicability of airborne gamma-ray spectrometric data to regional evaluation of radon hazard has been suggested. A case history on Antelope Island in the Great Salt Lake, Utah, is also presented, showing the role of radon surveys in construction planning.