A method of filtering in a radar reception chain of the ground and/or sea clutter echoes intercepted by the sidelobes of an airborne radar, said echoes being picked up in the distance-speed domain, said method being characterised in that it has: - a step of producing a mask (21, 52), in the distance-speed plane, overlying the zone of detection (10, 20) of the ground and/or sea clutter echoes picked up by said sidelobes, said zone (10, 20) being determinable by the antenna parameters of said radar, the waveform emitted by said radar and the environmental context of said radar, all the points of said distance-speed plane which are covered by said mask being assigned a characteristic which is specific to said mask; - a step of filtering the received echoes, in which the echoes covered by said mask (21, 52) are rejected from the radar reception processing; and in that the antenna parameters being the antenna pattern and the squint of the antenna, the environmental context being the position, the attitude and the speed of the carrier of said radar, step of producing said mask consisting in assigning the points of said distance-speed plane of said characteristic, said step has the following steps: - the antenna pattern is sampled in elevation according to a given angular sampling interval, the samples obtained corresponding to the main lobe and to the sidelobes of said pattern; - for each sample: - the pointing direction is calculated in the coordinate system of the antenna as a function of the angular parameters of the antenna squint; - a change of coordinate system is performed so as to express the pointing direction of the antenna in the NED (North/East/Down) coordinate system of said carrier, as a function of the position, of the attitude and of the speed of said carrier, as well as a function of the squint of the antenna; - the distance and the Doppler frequency of said sample is calculated on the basis of the NED coordinate system as a function of the parameters of the emitted waveform, said sample thus being positioned in the distance/speed domain; - said characteristic is allocated to said sample of the distance-speed plane if it corresponds to a sidelobe. - a step of producing a mask (21, 52), in the distance-speed plane, overlying the zone of detection (10, 20) of the ground and/or sea clutter echoes picked up by said sidelobes, said zone (10, 20) being determinable by the antenna parameters of said radar, the waveform emitted by said radar and the environmental context of said radar, all the points of said distance-speed plane which are covered by said mask being assigned a characteristic which is specific to said mask; - a step of filtering the received echoes, in which the echoes covered by said mask (21, 52) are rejected from the radar reception processing; - the antenna pattern is sampled in elevation according to a given angular sampling interval, the samples obtained corresponding to the main lobe and to the sidelobes of said pattern; - for each sample: - the pointing direction is calculated in the coordinate system of the antenna as a function of the angular parameters of the antenna squint; - a change of coordinate system is performed so as to express the pointing direction of the antenna in the NED (North/East/Down) coordinate system of said carrier, as a function of the position, of the attitude and of the speed of said carrier, as well as a function of the squint of the antenna; - the distance and the Doppler frequency of said sample is calculated on the basis of the NED coordinate system as a function of the parameters of the emitted waveform, said sample thus being positioned in the distance/speed domain; - said characteristic is allocated to said sample of the distance-speed plane if it corresponds to a sidelobe.