Because of the complexity and interconnection density of today's integrated circuit chips, experimental measurement of individual transistor or diode junction temperatures under typical powered conditions has become increasingly difficult. In order to provide meaningful thermal data, other approaches have had to be devised. In the work described by this paper, an analytical model has been used to determine the steady state junction temperature rise on an integrated circuit chip. The effect on junction temperature of heat source size, geometry, and number of adjacent heat sources has been studied. Experimental testing on specially prepared chips has verified the analytical results.