since the earliest results on the linkage between ras activation and cell transformation appeared a vast amount of additional information has been generated which emphasizes the importance of ras-related genes in membrane trafficking, cell proliferation, differentiation and cancer. These advances led to the development of new strategies for the diagnosis, prognosis and prevention of cancer. Ras-related genes appear to be central to the mechanism of transformation by other oncogenes and therefore constitute a focal point upon which attempts to intervene in the process of carcinogenesis will be concentrated. The present volume contains the contributions to the NATO Advanced Research Workshop on the The Superfamily of ras-Related Genes held in Agia Pelagia, Heraklion, Crete, Greece, May 1991. At this meeting the leading researchers in this field carne together to discuss the most recent progress in analysis of biological function of the ras-related genes. As an organizer I feel that the Workshop was a success, and would like to thank all the participants and the contributors to this volume. I thank the NATO Scientific Affairs Division, Brussels, the Greek Ministry of Industry, Energy and Technology, the International Center for Cancer Research, the National Hellenic Research Foundation and the Medical School, University of Crete for sponsoring the Meeting.