The cesium inorganic ion exchange material, ammonium molybdophosphate (AMP)/polyacrylonitrile (PAN) composite, was recently tested at the Idaho National Engineering and Environmental Laboratory (INEEL). Small-scale tests using a column having a bed volume of 1.5 mL were performed in a shielded hot cell with actual INEEL high-activity waste. Tests were also performed with an identical column using simulated INEEL waste spiked with 137Cs. These results show AMP-PAN to be very effective in removing 137Cs from ICPP acidic waste. A cesium decontamination factor of >3000 was achieved in the actual waste test. Tests with actual waste and simulant indicate the AMP-PAN composite to be regenerable and have a large capacity for cesium.