Separations of anions by isotachophoresis can be carried out in different ways. Differences in mobilities and/or differences in pK values can be used for the simultaneous separation of anions. The separations of anions, using both the differences in mobilities and/or the differences in pK values, were studied in this work. Experimental values for about one hundred anions are given. Equations are derived for the separation of anions in buffered systems and the experimental results are compared with calculated values in order to check the theory.