A flood of new information, from whole-genome sequences to detailed structural information to inventories of earth's biota, is transforming 21st century biology. Along with comparative data on morphology, fossils, development, behavior, and interactions of all forms of life on earth, these new data streams make even more critical the need for an organizing framework for information retrieval, analysis, and prediction. Phylogeny, the genealogical map for all lineages of life on earth, provides an overall framework to facilitate information retrieval and biological prediction. Currently, single investigators or small teams of researchers are studying the evolutionary pathways of heredity usually concentrating on phylogenetic groups of modest size and lower taxonomic rank. Assembly of a framework phylogeny, or Tree of Life, for all 1.7 million described species requires a greatly magnified effort by large teams working across institutions and disciplines. This is the overall goal of the Assembling the Tree of Life activity. The U.S. National Science Foundation invites research proposals from multidisciplinary teams to conduct creative and innovative research that will resolve phylogenetic relationships for large groups of organisms on the Tree of Life. Teams of investigators also will be supported for projects in data acquisition, analysis, algorithm development and dissemination in computational phylogenetics and phyloinformatics. Please see the Program Solicitation (NSF 03-536) posted on the NSF website http://www.nsf.gov in the Documents Online section) for description of the activity and guidance on proposal preparation; note the deadline of May 5, 2003.