This volume is a collection of the lectures presented at the NATO Advanced Study Institute Interfacial Aspects of Phase Trans- formations , held in Erice (Sicily) in 198t.The Institute was the seventh course of the International School of Crystallography, es- tablished in the Center of Scientific Culture Ettore Majorana in 1974, with the guidance and inspiration of L. Riva di Sanseveri and A. Zichichi. The course organizers, R. Kern and myself, were advised and helped in developing the program, and in the choice of lecturers and participants, by R.F. Sekerka, F. Bedarida, J.L. Katz and J. G. Dash. Although the scope of the Institute (as reflected in the content of this book) might appear too wide, we believe that it responds to a real necessity. Both Surface Science and Crystal Growth (in- cluding problems of nucleation, thin films, recrystallization etc.) have developed to an unusual extent during the last few decades. Each of these two fields have benefited from the kwledge of the other; good examples are the progress in evaporation/condensation thermodynamics and kinetics of organized (sub-)molayers, the de- velopement of new methods of preparing and characterizing atomical- ly smooth or controlled vicinal (stepped) surfaces, etc.