Total radiated heat loss and average surface temperature of living bodies have heretofore required laborious computation from numerous local measurements. The present study introduces the blackbody principle for this objective. Shieldless surface receivers have been designed, and built from identical and symmetrical sets of thermoelectric foil junctions, which were then made different only in their power to absorb or reflect radiation. By means of thermal shunting, they have been rendered stable against air motion up to 8 m/sec. A cavity, when uniformly lined with such receivers, will integrate the measurements of radiated output into every direction of space, permitting a direct recording of the total. The receivers have been developed specifically for application to the human gradient calorimeter now under construction. However, since the laws of radiation apply to cavities of any size or shape, the proper function of blackbody radiometry could be experimentally verified with a smaller number of receivers in a body of 8×8×16 cu. in. The 4π-measurement is practically independent of location, size, or shape of the emittent source. The sensitivity is 76 μv/cal./sec. Full response is attained within 2.4 sec.