Approximately1011electrons are trapped in a single stage 15‐kG magnetic mirror and compressed to a volume of roughly1 cm3. The trapped electron distribution function is peaked at 0.5 MeV and shows a spread of 0.45 MeV. A base pressure of5×10−8 mm Hginsures negligible neutralization of the electron cloud for about 2 msec. The trapped electron configuration has a low‐frequency (2MHz) precession motion about the magnetic axis.