The phase shift with incident angle of reflected ultrasonic waves incident near the Rayleigh critical angle is reported. These measurements substantiate the predictions of our model. These predictions differ substantially from previous theories which neglect attenuation. For frequencies above 15 MHz the slope of the phase shift of an ultrasonic wave reflected from a water‐stainless steel boundary reverses at the Rayleigh critical angle. For frequencies below 15 MHz the phase shifts from 0° to +360°; above 15 MHz it shifts from 0° to +60° then to −60° and back to zero again on passing through the Rayleigh critical angle. The sensitivity of this phenomenon suggests that it could be useful in determining or evaluating changes in material properties such as cold work, residual stress, or grain sizes.