"Progress is reported on Phase II of a program for the development of a mixed fission product fueled thermoelectric generator. Materials studies are described in which bonded assemblies of bismuth telluride were life tested up to 3000 hours at 350 to 400 deg F hot junction temperature. Data were too inconsistent to define any satisfactory long-life bonding process. Further work is needed to eliminate the process variables. Insulation studies aimed at determining the thermal conductivity of various insulations with different fill gases under reduced pressures are described. Opacified aerogel powder appears to be very promising as an insulation medium for a diffuse heat source. A full- scale simulated test generator aimed at proving out the concept of a diffuse heat source for power generation is described. Progress on the construction of this electrically heated generator and its thermoelectric power converter is related.