Conventional fluorometric and delayed-neutron counting techniques are those most widely used in geochemical exploration for uranium. Other techniques such as those based on X-ray fluorescence, laser-induced fluorescence and nuclear-fission track measurements are used to a lesser extent, but all have unique capabilities and may indeed experience greater use depending on sensitivity required, sample media, chemical form of uranium or associated daughter products, turnaround time, and initial costs of equipment. With solid materials, the sensitivities achieved by fluorometric method are of the order of 0.1–0.2 ppm; with liquid materials, the sensitivity of the laser-induced fluorometric method is of the order of 0.02–0.05 ppb, and that of the nuclear-fission track measurement technique is near 0.01 ppb. Techniques have been developed for rapid, automated, neutron activation analysis (NAA) of sediment and water samples for uranium and as many as 20 other elements. Uranium in water samples is extracted in the field onto ion exchange resin which is later analyzed by NAA. Tests show nearly complete removal of dissolved materials in most waters and selective removal of uranium even from high-conductivity waters. Detection limit for U varies with irradiation conditions but is normally about 0.02 ppb for water (on resin) and better than 1 ppm for sediment under Savannah River Laboratory routine operating conditions. Amid the overwhelming proliferation of instruments controlled by microprocessors for determining uranium in geologic materials, problems and limitations remain and when the instruments fail, a skilled analyst'can use one of several analytical procedures, albeit at a reduced output and greater expense.