Alkali aluminophosphate glasses, including those in the system xAl(2)O(3). (1-x)CsPO3 (0 less than or equal to x less than or equal to 0.25), were examined by highperformance liquid chromatography (HPLC), infrared (IR), and Al-27 magic angle spinning nuclear magnetic resonance (NIAS NMR) spectroscopies. Phosphate anions become progressively shorter with the addition of alumina to a metaphosphate glass. Al3+ ions are initially incorporated into the structure in octahedral sites, but the average Al coordination number (CN) decreases with increasing alumina content and tetrahedral species are the preferred moiety when [O]/[P] > 3.5, Al[4] sites appear to be associated with monophosphate (Q(0)) anions, The role of modifier size on aluminophosphate structure is investigated. At low alumina content (< 15 mol%), the disproportionation of pyrophosphate anions into triphosphate and orthophosphate anions is responsible for the lower average Al CN of cesium aluminophosphate glasses compared with sodium aluminophosphate glasses.