The central question of Comparative Immunology is how immune mechanisms have evolved. How do they change and adapt in response to the diverse microbial challenges present in the many and different environments that are occupied by animals? The tremendous diversity of animal life poses, in itself, a great challenge to such studies. Although it is clearly impossible (indeed counterproductive) to investigate the immune system of all animals, are we seriously restricting our knowledge by studying relatively few species? Are we missing important aspects of the diverse immune systems that function so effectively in animals? This workshop will discuss the current status and potential future developments of evolutionary immunobiology while coming to grips with the following two issues. First, are there model species that, while offering ease of experimental manipulation and/or potential economic importance, occupy key phylogenetic positions? Second, can the chosen model species be used to establish paradigms (the equivalent of the Rosetta Stone) through which evolutionary and immunological processes in other species can be interpreted? In addition, the final session of the proposed Workshop will deal with the application of concepts from evolutionary immunobiology to understanding and managing problems of infectious diseases that affect and alter ecosystems. Biology is going through a revolution resulting from the application of genome-wide approaches to understanding organisms. Results from those projects which have been, or are about to be, accomplished (including human, mouse, Drosophila, C. elegans, pufferfish, zebrafish) have demonstrated the extraordinary power of genomics to contribute to the solution of problems in genetics, and molecular cell biology. Genomic approaches yield detailed information about a species, answering questions and generating new hypotheses at a remarkable rate. Yet the advances to be gained from genomic approaches can go far beyond simple analyses of the genes present in any given species, and an understanding of the control of expression of those genes. For example, we now have opportunities to study evolutionary processes through comparisons between complete genomes. In addition, as patterns of organization become apparent at the level of the whole genome, we will be able to extrapolate efficiently and effectively from the findings in favored key species, to make novel and testable predictions about other species that have been studied less intensively. This workshop has, as a major theme, the actual and potential impact of genomics on the field of evolutionary immunobiology.