STRUCTURE AND STABILITY OF ALLOYS**This chapter is dedicated to the memory of my good friend Professor Peter Haasen. Much of the revision which I undertook was done in Göttingen, in the summer of 1993, and many suggestions for changes and improvements came from Peter during our walks in Göttingen woods. I am very grateful to the Alexander von Humboldt Foundation for the award of the Humboldt Prize which made my stay in Göttingen during that summer possible.