Calculations of surface wave and radar cross section modulation induced by a spatially varying surface current have been compared with field measurements made with synthetic aperture radar (X and L bands), real aperture radar (X band), laser slope gauge, and charge-coupled device video camera during the Joint Canada-U.S. Ocean Wave Investigation Project (JOWIP), which took place in August 1983. The comparison reveals that (1) many existing wind relaxation models underpredict the hydrodynamic effect of the current, (2) the simple Bragg scattering model underpredicts radar backscatter modulation for higher-frequency radars (e.g., X band) but appears acceptable at lower radar frequencies (e.g., L band), and (3) the discrepancy between measurements and calculations at high radar frequency is reduced, but not eliminated, when the effects of long surface waves have been accounted for. ¿ American Geophysical Union 1988