AbstractTwo models have been proposed which can be used to predict the occurrence of liquid immiscibility in ternary metallic alloys. One model, derived from an earlier proposal by Axon for predicting liquid immiscibility in binary alloys, was based on differences in the atomic sizes and melting points of the metals. The second model, based on a proposal made by Mott (from the binary metallic liquid immiscibility rule of Hildebrand and Scott), utilises solubility parameters and electronegativities as the determinants. The models were tested against the known behaviour of 27 metallic ternary systems which show liquid immiscibility and 36 systems which show either complete liquid miscibility or only a small region of liquid immiscibility confined to a region adjacent to an immiscible binary system. Both models showed good predictive ability when applied to the first group of 27 systems, but the first model proved to be superior when applied to the 36 miscible liquid systems. The behaviour of the liquid phase was always predicted correctly by one or other of the models in all the ternary systems examined.MST/1412