Direct experimental evidence is given to show that the traditional viewpoint of polarization reversal must be modified to include the path of consecutive non-180 • domain switching. Using ultrasonic waves, we have successfully monitored multi-domain formation during the polarization switching cycle in a bulk single crystal 0.955Pb(Zn 1/3 Nb 2/3 )O 3 -0.045PbTiO 3 . A model is proposed for the polarization reversal mechanism in this system. This model is supported by ultrasonic attenuation measurements.