FlyBase is an online bioinformatics database and the primary repository of genetic and molecular data for the insect family Drosophilidae. For the most extensively studied species and model organism, Drosophila melanogaster, a wide range of data are presented in different formats. Information in FlyBase originates from a variety of sources ranging from large-scale genome projects to the primary research literature. These data types include mutant phenotypes; molecular characterization of mutant alleles; and other deviations, cytological maps, wild-type expression patterns, anatomical images, transgenic constructs and insertions, sequence-level gene models, and molecular classification of gene product functions. Query tools allow navigation of FlyBase through DNA or protein sequence, by gene or mutant name, or through terms from the several ontologies used to capture functional, phenotypic, and anatomical data. The database offers several different query tools in order to provide efficient access to the data available and facilitate the discovery of significant relationships within the database. Links between FlyBase and external databases, such as BDGP or modENCODE, provide opportunities for further exploration into other model organism databases and other resources of biological and molecular information. The FlyBase project is carried out by a consortium of Drosophila researchers and computer scientists at Harvard University and Indiana University in the United States, and University of Cambridge in the United Kingdom. FlyBase is one of the organizations contributing to the Generic Model Organism Database (GMOD). the FlyBase home page requested a website access fee of US$150.00 per person per year, stating that "The NHGRI has reduced the funding of FlyBase by 50%". Background Drosophila melanogaster has been an experimental organism since the early 1900s, and has since been placed at the forefront of many areas of research. As this field of research spread and became global, researchers working on the same problems needed a way to communicate and monitor progress in the field. This niche was initially filled by community newsletters such as the Drosophila Information Service (DIS), which dates back to 1934 when the field was starting to spread from Thomas Hunt Morgan's lab. Material in these pages presented regular 'catalogs' of mutations, and bibliographies of the Drosophila literature. As computer infrastructure developed in the '80s and '90s, these newsletters gave way and merged with internet mailing lists, and these eventually became online resources and data. In 1992, data on the genetics and genomics of D. melanogaster and related species were electronically available over the