The effect of three low molecular weight quaternary ammonium hydroxides with different alkyl groups upon stabilisation of alumina aqueous suspensions is studied and compared with that of Tiron(R), a compound based on the benzene molecule. The purpose is to illustrate the effect of molecular structure and charge location upon dispersing effectiveness. Rheological and electrophoretic measurements using both bare and surface charge modified alumina were carried out. Tiron(R) revealed to be the most efficient dispersant for alumina in water.