The chromatographic separation of several pituitary proteins on a Mono-Q anion-exchange column is described. The effect of eluent pH and buffer composition on the resolution is demonstrated with several standard proteins. The experimental data indicate that good protein recoveries and resolution can be obtained on this essentially monodisperse microparticulate ion-exchange resin when the pH of the eluent is chosen ca. 0.5 pH units below the pI of the most basic component in the mixture. With this new column separations are ca. 30 times faster than with conventional cellulosic anion exchangers at similar sample loads.