Abstract: A clutter tracking and cancelling system, for use in a MTI radar system, comprising an auxiliary channel consisting primarily of a phase detector and a canceller. The phase detector provides an output which represents the phase difference between the IF and the coho output, while the output of the canceller, which responds to the phase detector output, represents clutter MTI residue from one transmission to the next. Clutter MTI residue from several successive range bins is smoothed and integrated to provide a control output which is used to shift the phase of the coho frequency, which is supplied to the phase detector in the conventional main MTI channel, to set the mean clutter velocity at zero velocity in order to produce optimum clutter cancellation in the main MTI channel.