Abstract : An analytical formulation of the bed shear stress coefficient inside the surf zone is derived using the concept of radiation stress. A truncated Rayleigh p.d.f. is used to describe the wave field inside the surf zone and provides the input to calculate the variation of wave energy and longshore current as a function of wave height, water depth and distance to shore. The wave set-up is approximated using a sinusoidal wave solution. Field measurements of longshore current and waves within the surf zone are used to calculate the bed shear stress coefficient. Frequency distributions and statistics are calculated for the bed shear stress coefficient.