The stability of a homogeneous plasma with currents along the magnetic field is investigated. It is found that electrons streaming along the magnetic field lines in a neutralizing positive ion background could excite lower‐hybrid instability. The critical drift velocity should exceed the parallel phase velocity for instability:Vd>&ohgr;r/k∥, where &ohgr;ris the lower‐hybrid frequency (&OHgr;e&OHgr;i)1/2. This condition is found to be easily met in the laboratory and space plasmas and is applicable both in the collisionless and collisional palsmas.