The procedure for obtaining the performance of a thermoelectric generator from a knowledge of the materials, properties, the junction temperatures, the leg geometries, and the extraneous circuit resistance are well known. This paper deals with the reverse procedure of designing a device which will perform in an optimum fashion while delivering a predetermined voltage and current from a given input heat flux density. The design procedure is demonstrated for hypothetical 250-W generator utilizing segmented N-type PbTe (type 3N/4N)* and P-type PbTe (type 2P). The optimized performance parameters of these materials under ideal conditions are presented in tabular form. Adjustment procedures are established to account for extraneous resistance, shunt heat losses, and off-optimum design performance. The design of the converter portion of a 560-W portable multifueled generator is reviewed, and the results are compared to observed performance.