It is generally accepted that even trained listeners have great difficulty perceiving static phase differences in two‐tone stimuli. However, if the waveform with the changed phase is “inserted” into a longer signal, most observers can reliably detect whether the change has been made. This study used this “insert” method to compare a series of waveforms which differed from a standard waveform by 15°, 30°, 45°, 60°, 75°, 90°, 102°, 150°, and 180°. The standard waveform wasA sin2π(250)t+B sin[2π(500)t+90]. By the time the comparison waveform differed from the standard by 60°, observers could perceive the phase change correctly on over 75% of the trials. An attempt is made to identify the cues which permit the system to recognize such nonenvelope phase changes, but the data do not permit positive identification of these cues.