Bremsstrahlung spectra and on‐axis depth‐dose distributions due to 25.5‐MeV electrons incident on seven different Ta and one Al radiator were studied, with and without beam‐hardening filters of Al and Pb. The photon spectra were measured with a gamma‐ray spectrometer consisting of a liquid deuterium target viewed by a time‐of‐flight detector of photoneutrons. A remote‐controlled, miniature ion chamber was used to measure depth‐dose profiles in a water phantom. The Ta radiators ranged in thickness from 0.012 radiation length up to 1.0X0. The thinner the radiator, the harder was the measured spectrum. The maximum forward yield was obtained for a thickness of about 0.3X0. The forward yield and spectral shape of the photon beam from 0.07X0of Al as radiator were very similar to those from 0.06X0of Ta. Beams produced in Ta radiators and filtered by 27.28 g/cm2of Al gave a harder spectrum than those filtered by 15.06 g/cm2of Pb. Total absorption cross sections of Al and Pb for photon energies between 4 and 24 MeV were obtained which agree with theoretical calculations, within measurement errors. The depths in water at which the dose fell to 0.5 of peak dose was greater when the Al filter was used than when the Pb filter was used. For end point energies greater than 10 MeV, beam‐hardening and field‐flattening filters should be made, if space permits, of low‐atomic‐number materials.