The justification for yearbooks is greater than ever as we approach the third millennium, overwhelmed with information. This first edition of the Cytokine Yearbook summarizes the latest advances in the revolutionary field of cytokine research. The work is not a comprehensive reference work, but covers a selection of current themes. The intention is to keep paying attention to current topics in the Yearbooks to come. The editors invited a number of distinguished colleagues, who are international experts in their specific fields, resulting in a high scientific level of the contributions. This Yearbook is required reading for every scientist and physician working in the field of cytokines.