The effect of surface drift velocity on the energy transfer from the wind to ocean waves and the growth rate of the dominant surface wave was studied analytically. The model analyzed considered first the airflow above the surface wave to be turbulent, the thin drift shear layer to be viscous, and the flow beneath the drift flow to be potential. Then an extension of the analysis was made for the case of a drift shear layer of considerable thickness. The analysis clearly demonstrated the important role that air turbulence and water surface drift play in the wind energy transfer to waves. It was also found that the exponential growth dominated the process of the wind energy transfer to waves. In general, the presence of surface drift increased the wave energy growth rate. The present analysis predicted the existence of a critical value of the normalized surface drift velocity, at which the increment of wave energy growth due to surface drift reached a maximum. When the surface drift exceeded the critical value, there was an adverse effect on the wave energy growth. In the extreme condition in which the surface drift matched the phase speed, it set up the upper limit of the wave energy growth rate. The numerical estimates computed with the theory were consistent with experimental measurements, and with the results obtained with more complex analyses based on numerical models. ¿ American Geophysical Union 1993