Polyacrylic acid (PAA) and starch represent two of the most widely used commercial flocculants in the mineral processing industry, Both are known to behave as selective flocculants in the beneficiation of iron ore slimes. This paper compares these two types of flocculants in achieving selective separation of iron oxide from clay, Our results indicate that PAA requires a lower flocculant dosage and yields bigger flocs, Starch is found to be more selective than PAA. Important differences in the behaviour of these two flocculants, as investigated with the help of a set of statistically designed experiments, are explained in terms of the proposed mechanisms of interaction of starch and PAA with iron oxide and clay, Electrostatic interactions play an important role in achieving selectivity.