The steady rate of heat conductionQfrom a heated sphere maintained at a constant temperature different from that of a surrounding two‐phase medium, which consists of an array of spherical particles of thermal conductivity &agr;kand a matrix of conductivityk, is determined by a method of multipole expansion toO(&fgr;4), where &fgr; is the volume fraction of the particles in the array, and by a lubrication analysis for highly conducting and closely packed arrays. The results of the two analyses are combined to obtain estimates ofQthat are expected to be accurate over the complete range of &agr; and &fgr;. These results are compared with the predictions of an effective‐medium theory, and it is shown that the predictions of this theory are quite accurate over a rather wide range of &agr;, 0<&agr;<103, for the case of a simple cubic array, even at its maximum allowable volume fraction, but differ by as much as 60% for the case of a face‐centered cubic array.