Geochemical data presented in this report pertain to Cretaceous igneous intrusions of the Boulder batholith and its satellitic plutons in southwest Montana. The geographic area addressed in this compilation is approximately bounded by lats 45.6 deg and 46.7 deg N. and longs 112.75 deg and 111.5 deg W. These data were compiled in order to establish the geologic framework for world-class mineral deposits of the Butte district. Although these deposits and their host rocks have been the subject of many investigations, the petrologic characteristics of associated intrusive rocks have not been systematically compiled, synthesized, or interpreted. Abundant late Mesozoic intrusions in the study area are probably byproducts of subduction-related processes, including back-arc magmatism that prevailed along the west edge of the North American plate during this interval. The ultimate goal of this effort will be an evaluation of the time-space-compositional evolution of Mesozoic magmatism associated with the Boulder batholith and identification of genetic associations between magmatic and mineralizing processes in this region.