This thesis (report of Contract No. G0122137) sets forth a practical method for evaluating underground sources of heat in deep mines and provides an improved information base. Seven topics for further research are recommended. The heat sources considered are wall- rock, ground water, adiabatic compression, equipment, service lines, blasting, metabolism, curing of cement, and oxidation of sulfides and timber. Seven deep metal mines with high production rates and high heat loads were visited to obtain data necessary to assess their thermal environments. Data analysis disclosed that rock heat and adiabatic compression account for about 60 percent of the mine heat load at depth.