It is shown that in general the stability of a hot‐electron‐stabilized symmetric tandem mirror is the same as the stability of its barrier‐plug cell alone, plus an additional limitation on the center‐cell length such that the center‐cell Alfve´n frequency is higher than the average barrier‐plugE×Bdrift and the hot‐electron precession frequency. The stability of the hot‐electron barrier‐plug cell is studied extensively.