An n-CdS(In)/p-Si heterojunction solar cell was fabricated by vacuum evaporation of a single source of a stoichiometric mixture of CdS and In on a p-Si single crystal wafer at a low temperature of 120 degreesC. The open circuit voltage, short circuit current density, fill factor and conversion efficiency under AMI were 0.47 V, 20 mA/cm(2), 0.74 and 7%, respectively. The physical and photoelectric characteristics were measured and discussed. In addition, the cell was irradiated by gamma radiation of 1.25 MeV and its effect on the cell performance was studied. Various preparation parameters such as composition and CdS layer thickness affecting the cell characteristics were investigated before and after exposure to the radiation.