Book excerpt: This book is a second edition of the one that was published by John Wiley & Sons in 1988. It carries a new title because the former one, A Primer of Diffusion Problems, gave the impression of consisting merely of a set of problems relating to diffusion. Nonetheless, my intention was clearly spelled out and it remains the same, namely, to teach basic aspects and methods of solution for diffusion phenomena through physical examples. Again, I emphasize that the coverage is not encyclopedic. There exist already several outstanding works of that nature, for example, J. Philibert's Atom Movements, Diffusion and Mass Transport in Solids. My emphasis is on modeling and methodology. This book should thus constitute a consistent introduction to diffusion phenomena, whatever their origin or further application. This edition has been largely revised. It contains a completely new chapter and three new appendices. I have added several new exercises stemming from my experience in teaching this material over the last 15 years. I hope that they will be instructive to the reader for they were not chosen perfunctorily. Although they are the bane of authors and of readers, I have retained footnotes if they might help the reader's comprehension. Additional, but nonessential material is collected at the end of chapters, and is indicated in the text by superscripts.