Measurements of the absolute noise power of highTcmultijunction flux‐flow amplifiers in the frequency range 0.1 Hz–60 kHz are reported. The noise is found to have maxima at the operating points corresponding to optimum transresistance and gain, and is consistent with existing models of critical current fluctuations as found in single grain boundary junctions. The frequency dependence of the noise power is usually close to 1/f, although a Lorentzian term is sometimes observed. The normalized values of measured critical current fluctuations are approximately temperature independent as previously found for single junctions prepared by similar techniques. ©1995 American Institute of Physics.