This book deals with the cellular surface of the parasite Trypanosoma brucei, which is responsible for human sleeping sickness and the nagana disease of cattle, two plagues of the African continent. In the mammalian blood-stream, the trypanosome evades the immune defenses of the host through a continuous variation of its major surface antigen, the VSG (Variant Surface Glycoprotein). The first part of the book is devoted to the study of the genetic mechanisms involved in this process of antigenic variation. The second part is focused on the genetic mechanisms underlying the changes of surface proteins which occur during the life-cycle of the parasite, alternating between the tsetse fly and the mammal. Finally, our knowledge about the surface receptors of trypanosomes, as well as their possible vaccination potential against trypanosomiases, is discussed.