Use is made of the concept of the frequency response function to analyse long-wave oscillations of the surface of a closed lake which is subject to forcing by tangential wind stresses. By comparison of a response function calculated from data taken from the North Coorong-an almost land-locked lagoon south-east of Adelaide, South Australia-with the theoretical, one-dimensional response calculated for a rectangular, constant-depth lake with dimensions equivalent to the average dimensions of this body of water, an estimate is made of the damping parameter for the lagoon. Predictions of wind-induced water level changes using the response function method agree well with recorded values.