In the present work the influence of the addition of some dispersing agents employed for maximizing the solid loading of alumina concentrated suspensions has been investigated. Three commercial deflocculants were used: a sodium salt of a benzenedisulfonic acid ( Tiron), a sodium polyphosphate, and an aurintricarboxylic acid, triammonium salt ( Aluminon). Rheological tests were carried out at 25 degrees C under continuous flow conditions by using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device SV2P with serrated surfaces. The application of rheological techniques permitted evaluating the efficiency and optimum dosage of the dispersing agents employed on the alumina slips examined, i. e., the critical concentration at which the maximum reduction in viscosity is detected.