The value of airborne radioactivity surveys in guiding U exploration has been well established. Improved circuitry and development of semiquantitative analytical techniques now permit examination of more complex geologic problems. It is shown that the airborne technique can be used in exploration for Th-bearing heavy mineral deposits and for uraniferous phosphorites. The observed radiation intensity and configuration of the gamma radiation field may be used to approximate the equivalent U content and extent of the surficial part of such deposits. The equivalent U content of infinite sources can probably be determined within a few thousandths of a percent and the boundaries fixed within a few hundred feet. As the areal extent of the source decreases, the accuracy of the analytical results likewise decreases.