Résumé : The preparative aspects of immobilized pH gradients applied to abnormal haemoglobins (Hb) is described. As shown with the example of Hb San Diego, this method is successful even with as small a difference in pHi as 0.01 pH unit. For characterization of such neutral variants, reversed-phase high-performance liquid chromatography is demonstrated to be a very efficient tool. © 1984.