Spectral power density from Cerenkov radiation was measured in the vacuum ultraviolet from 2000 to 620 A˚. The radiation was produced by passing a 500‐MeV 1‐mA‐peak‐current electron beam through 1.4 m of 1 atm of helium gas at room temperature. In the photon energy range from 6 to 20 eV, approximately 1014photons /sec/A˚/mA of electron‐beam current were emitted, and our detection apparatus attenuated the radiation by 4–5 orders of magnitude.