The ion-exchange selectivity of H+-form of cubic ammonium molybdate (H-CAM) was studied for alkali metal ions in both HNO3 and NH4NO3 media. Ideal ion-exchange reaction was observed in both the media with high selectivity for Rb+ and Cs+. The selectivity sequence was found to be Li+ < Na+ < K+ < Rb+ < Cs+ in accordance with the Eisenman sequence-1 in both the media, with separation factors greater than the commercial polystyrene strong acid exchange resin. Efficient separation of alkali metal ions could be achieved on H-CAM column.