A method of epithermal neutron activation analysis for uranium and thorium is discussed in relation to other rapid analytical methods for these elements. Caledonian granites are divided into four main groups on the basis of U and Th contents: (a) a group of evolved late granites with high U and Th contents and high Th/U ratios, (b) a group of uranium-enriched mineralized granites, (c) granites containing approximately average levels of U and Th, and (d) a group of granites with low thorium content.