After the fundamental work of Borel and Chevalley in the 1950s and 1960s on the structure and classification of semisimple algebraic groups over an arbitrary algebraically closed field, further results were obtained on conjugacy classes and centralizers. Conjugacy Classes in Semisimple Algebraic Groups draws together results achieved by Lusztig, Richardson, Spaltenstein, Springer, Steinberg, and others. This book provides a unified exposition of work done over the past thirty years.