Abstract: At Köprübaşı most of the uranium deposits occurring in tabular lenses in conglomerates and sandstones of the Neogene alluvial fan are oxidized. These deposits can be divided in jarosite - vaylandite - rich andilmenite - magnetite - rich types both of which occur near exposures of metamorphic basement rocks. The unoxi-•dized uranium deposits are called as pyrite - siderite - rich type. Uranium is disseminated in the matrix of conglomerates and sandstones.Uranium contents found by laboratory gamma - ray spectrometric measurements are mostly much higherthan those found by fluorimetric analysis. Radiometric uranium contents (eU) in most deposits are 30 to 40 % greater than those of chemical uranium (U). Thorium contents found in the same deposits range between 40 to 340ppm.Therefore, ore grades in the deposits obtained by the gross gammabore hole techniques are, in fact, the total of radiometric uranium (eU) and thorium contents. Under the light of these data, the reserves of the uraniumdeposits in the Köprübaşı area must be reconsidered.