Chemical, mineralogical, and autoradiographic techniques applied to the study of five weathering profiles developed on granitic rocks of Oklahoma and Georgia indicate that mineral stabilities generally follow the expected sequence: plagioclase, biotite, K-spar, quartz, from least to most stable respectively. Kaolinite is the dominant clay mineral in the Georgia profile; both illite and kaolinite are major constituents in the Oklahoma profiles. Stability diagrams indicate that the Georgia surface waters are in equilibrium with kaolinite and the Oklahoma surface waters are in equilibrium with kaolinite and montmorillonite, but not illite. The largest physical and chemical changes occur in the transition from the C- to the B-horizon. Ca and Na are mobilized in the early stages of weathering, whereas K and Rb are concentrated in the relatively stable K-spar