This volume will include mini-reviews derived from work to be presented at the Aegean Conference: Second Crossroads between Innate and Adaptive Immunity, in Crete, Greece, June 17-22, 2007. This meeting is designed to serve as a forum to discuss the most recent progress in complement research as it pertains to human disease pathogenesis and therapeutics. The rapid pace of development in complement basic research and the advent and application of new experimental approaches in this field have now allowed us to take an integrated view of the in vivo biology of the complement system. The availability of new reagents (e.g. synthetic and recombinant inhibitors) and animal models (e.g. transgenic and knockout mice) has enabled us to address, in an in vivo setting, its involvement in various pathophysiological conditions. Such studies are shedding new light on the pathogenetic mechanism of complement-related diseases such as autoimmune diseases and inflammatory tissue damage as well.