[en] Radiometric methods of uranium prospecting have acquired great importance on account of the high demand for uranium as power reactor fuel and the possibility of their use for geological and structural studies. The concentration of uranium in the deposits is generally of the order of 0.1% or less. Such a low concentration may go undetected by the geologist's magnifying glass when examining the samples. Fortunately, uranium and its decay products emit gamma rays which can be detected by special instruments. Described here, for the benefit of the field geologist using such instruments, are the basic concepts and applications of the different types of instrumentation for the detection and analysis of potassium, uranium and thorium concentrations from aircraft, vehicles and boats, by borehole logging and in outcrops and laboratory samples. (author)