The observation of photorefractive two‐wave mixing bistability without external feedback is reported. Hysteresis with an on/off contrast ratio of 30 was obtained through the interaction of two 514.5 nm laser beams within a Fe: KNbO3crystal. A signal beam modulation rate less than 25 mHz was necessary to obtain the hysteresis when the total optical irradiance of the pump and signal beams was ∼1 mW/mm2. The data are shown to correspond well with a two‐state increasing gain model. ©1996 American Institute of Physics.