An experimental investigation of vertical mixing induced by wind,or by a screen which moved horizontallyover the water surface, was carried out in a wind-wave channel similar to that of Wu [27].It was found that,in the wind-wave channel, the entrainment rate due to the shear stress, which wasexerted on the water surface by the moving screen, was two orders of magnitude smaller than the oneobtained in similar experiments, which were carried out in an annular tank by Kato & Phillips [11],Kantha [9], and Kantha et al [10].