Abstract Two approaches are described to classify aerial radiometric data. The first procedure establishes categories that may correspond with recognized lithologic types, and the second method permits samples to be classified as possible U host or source rocks in the context of mineral-deposit models. The study is based on published analytical data for Th, U, and K concentrations in igneous rock samples and on aerial gamma-ray spectrometer data from the Basin and Range region and the Denver NTMS Quadrangle. The latter data were obtained as part of the U.S. Department of Energy National Uranium Resource Evaluation (NURE) Program. The results for the Basin and Range region are compared with estimates of world abundances for Th, U, and K for various lithologic types. The study demonstrates that radiometric classification of “formation” data and “outcrop” data into lithologic categories can be accomplished in arid regions based on highsensitivity, aerial gamma-ray spectrometer measurements of Th and K. The methods make it practical to use the gamma-ray data to estimate geochemically the degree of regional U enrichment, or depletion, with respect to, Th or K in the search for uraniferous provinces and potential U source or host rocks.