This paper presents experimental and theoretical work on the behavior of rf currents in electron beams which possess a spread of dc velocity. Experimentally an attenuation or damping of rf current with distance is noted. This attenuation is studied as a function of both velocity spread and space charge. Simple ballistic theory suffices to explain the damping rate for the first half space‐charge wavelength. A more exact distribution function analysis fails to give agreement much beyond this point. Qualitative disagreement with the exact theory occurs at a distance of one space‐charge wavelength. Here distribution function theory predicts a recovery of the current maximum over its previous value whereas experimentally monatonic damping is found. The failure of distribution function analysis to explain the observed current behavior in this simple case makes the validity of its application to the noise problem in microwave tubes somewhat questionable.