Propagation of a charge‐neutralized ion beam, in a transverse magnetic field (Bz<400 G) and in a magnetized plasma, has been studied. Measurements indicate that the beam propagation mechanism is due to theE×Bdrift in the region of high &bgr; (1<&bgr;<400), where &bgr; is the ratio of beam kinetic energy to transverse magnetic field energy. Diamagnetic measurements, both internal and external to the propagating beam, confirm the fast diffusion ofBzinto the beam on a time scale much shorter than the beam rise time of 10−7s. When the beam is injected into a magnetized plasma the electric field is shorted to a degree that increases with increasing background plasma density. When the plasma density reaches 1013/cm3(∼200×the beam density) complete shorting occurs and the beam is deflected by the transverse magnetic field.