A solar thermophotovoltaic (STPV) power system has attractive attributes for both space and terrestrial applications. This paper presents the results of testing by McDonnell Douglas Aerospace (MDA) over the last year with components furnished by the NASA Lewis Research Center (LeRC) and the National Renewable Energy Lab (NREL). The testing has included a large scale solar TPV testbed system and small scale laboratory STPV simulator using a small furnace. The testing apparatus, instrumentation, and operation are discussed, including a description of the emitters and photovoltaic devices that have been tested. Over 50 on‐sun tests have been conducted with the testbed system. It has accumulated over 300 hours of on‐sun time, and 1.5 MWh of thermal energy incident on the receiver material while temperatures and I‐V measurements were taken. A summary of the resulting test data is presented that shows the measured performance at temperatures up to 1220 °C. The receiver materials and PV cells have endured the high temperature operation with no major problems. The results of this investigation support MDA belief that STPV is a viable power system for both space and terrestrial power applications. ©1996 American Institute of Physics.