Electrostatic modes on non‐neutral electron clouds confined in a magnetic mirror field have been investigated. The cloud contains 2×1011electrons at an average kinetic energy of 0.3 MeV for a magnetic field with a peak intensity of 9 kG at the midplane. It was found that the cloud is moving azimuthally as well as longitudinally. The azimuthal motion has anm=1 spatial nature. The longitudinal modes have a more complicated nature, but their frequency equals that of the azimuthal mode.