It has been shown that the aluminum alloy 6061 in the fully annealed, cold-worked, and age-hardened conditions undergoes very small changes in the tensile properties as a result of neutron irradiation to doses on the order of 1019 fast n/cm2( > 2.9 MeV) and 1020 thermal n/cm2. At irradiation temperatures above 115°C, no changes in properties are observed. The small property changes observed when the material is irradiated at 43°C are mostly annealed out after ½ at 200°C. These changes are rationalized in terms of the precipitate particles present in the alloy and the mobility of the irradiation-induced defects.