The field of graph theory has undergone tremendous growth during the past century. As recently as the 1950s, the graph theory community had few members and most were in Europe and North America; today there are hundreds of graph theorists and they span the globe. By the mid 1970s, the subject had reached the point where we perceived a need for a collection of surveys of various areas of graph theory: the result was our three-volume series Selected Topics in Graph Theory, comprising articles written by distinguished experts and then edited into a common style. Since then, the transformation of the subject has continued, with individual branches (such as chromatic graph theory) expanding to the point of having important subdivisions themselves. This inspired us to conceive of a new series of books, each a collection of articles within a particular area of graph theory written by experts within that area. The first three of these books were the companion volumes to the present one, on algebraic graph theory, topological graph theory and structural graph theory. This is thus the fourth volume in the series.

A special feature of these books is the engagement of academic consultants (here, Bjarne Toft) to advise us on topics to be included and authors to be invited.We believe that this has been successful, with the result that the chapters of each book cover the full range of area within the given area. In the present case, the area is chromatic graph theory, with chapters written by authors from around the world. Another important feature is that, where possible, we have imposed uniform terminology and notation throughout, in the belief that this will aid readers in going from one chapter to another. For a similar reason, we have not tried to remove a small amount of material common to some of the chapters.

We hope that these features will facilitate usage of the book in advanced courses and seminars.