On the basis of a hydrodynamical theory of the acoustoelectric interaction (Fleming-Rowe) reported earlier which included electron inertial terms it is found that for sufficiently large electron drift velocities sharp high-gain peaks occur. Furthermore the peak values of gain achieved greatly exceed the maximum gain of the corresponding theory of Steele. Excellent agreement with recently reported experimental measurements of microwave acoustic gain in InSb is obtained. It is also noted that for large applied fields, empirical field factors are required to give agreement with experiment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70684/2/APPLAB-18-3-96-1.pd