The authors report the first results experimentally demonstrating the ability of a reconfigurable mesh reflector to adaptively form a null in the sidelobe region of an arbitrarily shaped pattern, with no a priori knowledge of the angular location of the source of interference. Using a prototype mesh reflector antenna with additional hardware and software in a compact antenna test range (CATR), deep nulls have been successfully formed for a number of simulated scenarios and some typical results are presented. It is shown that a null may be formed to a depth of –60 dB with respect to the pattern peak after less than 50 iterations of the nulling algorithm. It is believed that this represents the first demonstration of adaptive nulling using control of a reflector surface rather than the excitations of array or feed array elements.