On occasion, the amplitude of the pattern produced by a radio star on the record of a phase‐switching interferometer is observed to decrease. The interpretation of these fade‐outs is discussed, and they are shown to be caused mainly by phase scintillations. Simultaneous observations of fadeouts on two 53‐Mc/s phase‐switching interferometers having antenna separations of 25 and 50 wavelengths show that many of the fadeouts are caused by phase fluctuations having scales of a few hundred meters, and rms amplitudes of one or two radians. These irregularities appear to accompany rather than supplant the large‐scale irregularities normally associated with radio star scint