The ordering and stabilization behaviour of a set of CuAlNi alloys with manganese and boron additions have been studied. Specimens were subjected to different thermal treatments, mostly consisting of a direct quench into martensite from different temperatures. The transformation was studied by differential scanning calorimetry, and X-ray diffraction was also used to check the martensite and parent phase structures. According to the results, the first reverse transformation after quenching into martensite stems from two competitive processes, namely the stabilization of the martensite and a decrease of the transformation temperatures due to quenched disorder. The temperature from which the quench is performed is the critical parameter determining whether stabilization or disorder suppression predominates. The degree of stabilization increases with the manganese content.