Methods for the determinations of cesium, rubidium, and potassium were developed. For cesium this employed dissolution of finely ground samples, ion-exchange enrichment, and flame photometric determination. Rubidium and potassium were determined by flame photometry directly after dissolution. Data was obtained on 75 samples of granites, syenites, granodiorites, monzonites, diorites, tonalites, gabbros, and other rock types from seven North American batholiths. The average cesium content was found to be 6.6 p.p.m., and the data showed an apparently lognormal distribution. The overall K/Cs and Rb/Cs ratios were determined as 4800 and 26 respectively.