The stability of colloidal alumina in an aqueous suspension containing 10(-3) N KCl, 3 X 10(-4) N AlCl3 and polyacrylic acid was followed over 6 weeks. The concentrations of polymer, aluminum ions, and hydrogen ions in solution and the zeta potential of the colloid-polymer complexes were determined, while the initially predominant aggregation and subsequent fragmentation processes were monitored using a particle-counter technique. The size frequency curve c(n, t) vs n enabled the weight S(t) and number N(t) average sizes of the aggregates to be calculated and the kinetics of aggregation and fragmentation to be described. The colloidal stability of the system was found to vary with time and to be strongly correlated to the polymer dosage, the stability/instability threshold being fixed by the charge characteristics of the interfacial polymer layer. This experimental system could be appropriate for schematizing some natural systems involving partially soluble oxides and polymeric organic materials.