Caenorhabditis elegans (C. elegans) allows exhaustive analysis of animal biology, in detail once thought possible only for microbial organisms. This detail includes the entire cellular lineage from egg to adult, the complete adult cell complement, a full wiring diagram of the nervous system, and several hundred gene mutants that produce classical phenotypes. With the rise of genomic sequencing and functional genomics, analysis of C. elegans has grown to include reverse genetics, microarray assays of gene expression, and protein-protein interactions. Such studies should soon touch upon all ∼19,400 predicted C. elegans proteins and their detailed expression patterns. This should illuminate, but also complicate, our understanding of C. elegans cells and genetic pathways. Moreover, the newer forms of analysis are explicitly directed at acquiring data that are highly valuable with computational analysis but unintelligible without it. We describe the existing data sets and databases for C. elegans, and discuss ways in which large C. elegans data sets may be integrated.