А laboratory study of microwave reflection by swell and wind wave fields Experiments conducted in the IMST large Wind-Wave facility using principally the CNES RAMSES II radar device led to initial results on the identification of the phases of swell and wind-wave motions which contribute to the microwave (C and K bands) reflection. For geometrical reasons or non-linearity of the wave profiles, the reflection by the wave troughs appeared larger than the reflection by the wave crests. The reflection was seen to be dependent upon the presence of wavelets propagating along the swell or the dominant wind-wave profile. When the swell or the steepness of the wind waves is high enough to lead to local breaking, а large local enhancement of the reflected microwave occurs. The contribution of this particular event may even become predominant when its rate of occurrence increases. This is the case at high wind velocity.