The radial distribution of a noneutral electron cloud confined in a magnetic mirror was measured. The cloud is compressed by the magnetic field to a final radius of 4 mm from an initial radius of 4.5 cm with a final kinetic energy of 0.3 MeV and 2 x 10/sup 11/ electrons. The radial distribution of the cloud is hollow up to 150 ..mu..sec after injection. When the cloud is neutralized by a background plasma, filling in of the center does not occur.