Biotites from several Basin and Range monzonitic stocks have been analyzed for Cu, Pb and Zn. These data have been compiled for biotites from the Tintic, Bingham, Park City-Little Cottonwood, Iron Springs, San Francisco and related districts, the Gold Hill mining district, also the Mineral Range stock, and the Ibapah stock, all in Utah. Similar data have been compiled for the Ely district and the Whitehorse Pass stock in Nevada. The biotites were analyzed spectrochemically on an Applied Research Laboratories, 1.5 m, 24,000 line per in. grating spectrograph. In was used as an internal standard. The F test was used to establish the equivalence the variances of base metal concentrations in biotite from groups of individual stocks or districts. A graphical comparison of geometric means and standard deviations of the base metal content of biotites from the individual stocks and districts was examined and visual estimates of differences and similarities were noted. The comparisons show the following correlations: 1) Each stock or district belongs to its individual trace base-metal concentration population. 2) Contrasting correlations exist between base-metal concentration of biotite and base-metal production in the sampled areas. High Cu content is associated with Cu production, whereas low Pb and Zn content is associated with Pb and Zn production. 3) Biotites from hydrothermally altered stocks contain more Cu and less Pb and Zn than unaltered stocks. 4) Trace base metal content of biotite is an indicator of base metal mining districts in the Basin and Range province.