Radiation-induced solute segregation in molybdenum-rhenium solid-solution alloys was studied during elevated-temperature He- and Ne-ion irradiation. Segregation of Re atoms toward the external surface was measuring during irradiation by in situ Rutherford backscattering spectrometry. The amount of solute transported toward the irradiated surface is reported as a function of irradiation dose, dose rate, temperature and primary-recoil energy. The results of the segregation measurements agree with a theoretical model based on point-defect driven transport of the undersize Re atoms toward point-defect sinks. The relative efficiency for producing freely-migrating point defects decreases strongly with increasing primarily-recoil energy.