A summary of the activity performed in the investigation of metallic alloys over many years is presented. General attention is given to research carried out by using thermoanalytical techniques and their application to the determination of phase diagrams. The results obtained in the systematic investigation of several binary and ternary systems involving rare earth metals are briefly outlined and discussed within a more general picture of the alloying behaviour of these metals. A report with reference to the groups of alloys especially investigated and to a number of experimental difficulties encountered and solutions adopted is given.