The selectivity of two hydroxide-selective ion chromatography stationary phases was examined with varying solvent composition. The solvents acetonitrile 2-propanol and dimethylsulfoxide were found to diminish retention of these anions. However, retention times were found to increase for small anions with increasing methanol composition. For somewhat larger anions such as perchlorate and tetrafluoroborate, moderately decreasing or stable retention times were observed with increasing methanol content. The loss of retention is attributed to hydroxide form resins preferentially imbibing water from the solution phase, effectively increasing the elution strength of hydroxide because of its greater hydration energy. In methanol-water mixtures to 40%, these types of anion exchangers are known to swell to nearly the same extent (volume) as in water. Thus, hydration energy differences between hydroxide and these anions may not be as pronounced relative to weaker solvation in methanol. Run time for common inorganic anions on a high-capacity anion-exchange column can be reduced from 30 to 10 min through the use of acetonitrile. In addition, as the acetonitrile content is increased, retention reversals such as bromide-nitrate and chloride-nitrite occur. Four divalent species (sulfite, maleate, sulfate, fumarate) that are not separated on Dionex IonPac AS11 with hydroxide can be separated on the same column easily in 50% methanol.