The fate and transport of dissolved contaminants are largely determined by the degree of contaminant interaction with mineral surfaces. Compounds with high sorption affinity for the mineral phases present are retarded compared with groundwater flow. To reduce the uncertainty in modeling the transport of radionuclides and other contaminants at the Project Shoal Underground Test Area, near Fallon, Nevada, USA, a parametric sorption study with three cations (lead, strontium, and cesium) and two anions (selenite and chromate) was conducted. The granite from the Project Shoal Test Area was characterized and used for equilibrium sorption experiments in simple electrolyte matrices and synthetic groundwaters from the test area. Lead displayed a typical cation sorption behavior with fractional uptake increasing with increasing pH. In addition, lead sorption was essentially ionic strength independent, suggesting strong binding and substantial retardation under these conditions. Sorption experiments with strontium could not be performed, because of the high strontium content of the rock. Sorption of cesium was weakly pH dependent, suggesting sorption on cation exchange sites. Chromate and selenite displayed typical anion sorption behavior. For both anions, it appeared as if increased ionic strength resulted in increased fractional uptake. Parameters describing linear and Freundlich isotherms were estimated for a variety of conditions. Context abstract: The fate and transport of contaminants dissolved in ground- and surface waters are largely dependent on the degree of contaminant interaction with the mineral surfaces present in the flowpath of the water. The degree of interaction depends on a number of factors including mineral composition, solution composition, pH and temperature. Changes in geochemical conditions may have dramatically different effects on the behavior of different ions. Contaminant transport models using sorption parameters that are outside their range of applicability may, therefore, lead to substantial errors in the prediction of contaminant migration. To minimize the uncertainty in radionuclide migration modeling at the Project Shoal Underground Test Area, near Fallon, Nevada, USA, a parametric sorption study with three cations (lead, strontium and cesium) and two anions (selenite and chromate) was conducted. The results clearly indicate that lead sorption was strongly pH dependent, whereas cesium sorption was almost pH independent. In addition, because of the high strontium content of the granite, strontium, a cation considered reactive in most geochemical environments, appeared to be very mobile. Although the sorption isotherm parameters derived are applicable only to the specific material and ions, this study clearly demonstrates the importance of detailed aquifer characterization studies and experimental studies that quantify the effects of changing geochemical conditions on sorption.