The radiation resistance of GaInP/GaAs cascade solar cells grown by molecular beam epitaxy (MBE) was tested onboard Equator-S satellite. The short-circuit current, open-circuit voltage, and power data mere obtained for a period of about half a year. The remaining factors of these parameters were determined at the standard end-of-life (EOL) condition of an equivalent dose of 1 x 10(15) cm(-2) 1 MeV electrons. Electron irradiation tests were also performed in the laboratory. Consistent results were obtained with flight and laboratory data. The remaining power at the EOL condition was 0.89-0.90 for these cells, (C) 2001 Elsevier Science B.V. All rights reserved.