The detailed behavior of a solid cylindrical electron beam focused by a uniform magnetic field (Brillouin flow) has been studied experimentally. These studies include the influence of the optics of the electron gun on the beam‐focusing characteristics, the effects of transverse ``thermal'' velocities, the change in the internal beam dynamics with increasing values of magnetic focusing field, etc. A simple model of the beam is used to explain certain of the observed characteristics. It is found that an optically good electron gun will produce a focused beam which closely resembles the theoretical Brillouin‐flow model. A brief analysis of the electron motion in a magnetically focused beam is given in the Appendix.