Miniature tensile specimens of high purity iron and iron-copper alloys containing 0.1 and 0.3 weight percent copper were irradiated at 150°C and 290°C in the HFIR to 0.025 and 0.1 dpa. Following irradiation, room temperature tensile tests were performed. The effect of copper content on the yield stress (YS), ultimate tensile strength (UTS), uniform elongation (UE), and total elongation (TE) were examined for both unirradiated and irradiated specimens. For the unirradiated specimens, YS and UTS increased by 10% or less when copper in the amount of 0.1% was added, while UE decreased by about 30% and TE decreased by about 20% when copper in the amount of 0.1% was added to the pure iron. There was almost no further change in tensile properties when the copper content was increased from 0.1% to 0.3%. The effect of irradiation at 290°C to 0.1 dpa was to increase the strength and decrease the ductility of all the materials. Greater percent changes in tensile properties were observed in the Fe-XCu alloys after irradiation suggesting that copper contributes to the formation of extended defects at these temperatures.