For the past few years, the international research community has been generating genetic and genomic data and reagents for the model systems, X. tropicalis and X. laevis . These products include: 1) cDNA libraries and EST sequences, 2) UniGene clusters, 3) full-insert cDNA clones and sequences, 4) a genetic map, 5) genomic libraries and genomic sequences, 6) a physical map, 7) genome sequence, 8) microarrays, and 9) transgenic and mutant animals (see http://www.nih.gov/science/models/xenopus). These diverse data and reagents are being generated by investigators from several different research communities, including geneticists, gene sequencers, gene mappers, cell biologists, developmental biologists, and bioinformatics experts. These materials and data can now be used to enhance Xenopus' role as a model system. This PAR solicits applications from investigators in these different fields to combine these data, reagents and methodologies to elucidate the genetic basis of cell biological events, including embryonic development and organogenesis.