The optical attenuation induced in polymer‐clad silica fiber‐optic waveguides by low‐dose ionizing radiation (0.5–14 MeV) has been found to be much greater than expected on the basis of previous high‐dose measurements. The radiation sensitivity is dependent upon the purity and OH content of the silica and upon the radiation history of the fibers, but it does not appear to depend upon the drawing conditions nor on the limited radiation‐induced loss in the polymer cladding. The damage is greater at short times following the irradiation, and the decay kinetics of different synthetic silica fibers are qualitatively the same.