A simple method for generating plane Couette flow is described. In this technique the water surface of a covered open-channel flume represents the moving boundary, and measurements are performed in the overlying (sandwiched) air layer. Experimental results are presented which suggest transition from laminar to turbulent plane Couette flow at a Reynolds number (based on center-line velocity and channel half-depth) of about 280. Turbulent mean velocities from all available sources are correlated in terms of inner and outer law coordinates, and universal skin friction laws are derived therefrom for the case of hydrodynamically smooth boundaries. However, it is concluded that none of the presently available experimental data on turbulent plane Couette flow render support for von Kármán's theory of homologous turbulence. Results of a cursory exploration of the effects of unilateral boundary roughness suggest that mean-flow characteristics on the smooth side of a Couette channel assume the features prevailing on the rough side.