Unusually fast mutually pumped phase-conjugation (MPPC) is achieved in aBi12TiO20crystal by using transient photorefractive beam coupling under a dc electric field. Pulses of phase-conjugate waves with a buildup time of 4.5 ms and a width of 50 ms at an input intensity of 2×0.8W/cm2are obtained after applying a rising front of external electric field to the crystal. A phase-conjugation efficiency as high as 25&percent; of the incident light power is measured. ©1997 American Institute of Physics.