DAVID is a web-based tool for the functional annotation and visualization of gene lists. It integrates functional genomic annotations with intuitive graphical summaries, enabling the interpretation of genome-scale datasets by facilitating the transition from data collection to biological meaning. The tool allows users to rapidly annotate and summarize gene or protein identifiers based on shared categorical data for Gene Ontology, protein domain, and biochemical pathway membership. DAVID provides exploratory visualization tools that promote discovery through functional classification, biochemical pathway maps, and conserved protein domain architectures, while remaining linked to rich sources of biological annotation. DAVID's functionality is demonstrated using the Affymetrix GeneChip data of Cicala et al. The system architecture includes an automated procedure written in Microsoft Visual Basic (VB) 6.0 that updates DAVID weekly with public data from various sources. The data is parsed, formatted, and imported into an Oracle 8i relational database management system (RDBMS). DAVID includes four main modules: Annotation Tool, GoCharts, KeggCharts, and DomainCharts. The Annotation Tool provides several annotation options and builds a tabular view of the users' gene list and the available annotations. GoCharts graphically displays the distribution of differentially expressed genes among functional categories using the controlled vocabulary of the Gene Ontology Consortium (GO). KeggCharts graphically display the distribution of differentially expressed genes among KEGG biochemical pathways. DomainCharts display the distribution of differentially expressed genes among PFAM protein domains. DAVID is compared with related programs such as ENSMART, FatiGO, GeneLynx, GoMiner, MAPPFinder, MatchMiner, Resourcerer, and Source. DAVID combines features of both exploratory tools and annotation tools, providing a comprehensive set of data-mining tools that systematically combine functionally descriptive data with intuitive graphical displays. DAVID's functionality is demonstrated using the Affymetrix GeneChip data of Cicala et al. The tool is designed to facilitate the functional annotation and analysis of any list of genes encoded by human, mouse, rat, or fly genomes. DAVID provides automated solutions that enable researchers to rapidly discover biological themes in large datasets consisting of lists of genes.DAVID is a web-based tool for the functional annotation and visualization of gene lists. It integrates functional genomic annotations with intuitive graphical summaries, enabling the interpretation of genome-scale datasets by facilitating the transition from data collection to biological meaning. The tool allows users to rapidly annotate and summarize gene or protein identifiers based on shared categorical data for Gene Ontology, protein domain, and biochemical pathway membership. DAVID provides exploratory visualization tools that promote discovery through functional classification, biochemical pathway maps, and conserved protein domain architectures, while remaining linked to rich sources of biological annotation. DAVID's functionality is demonstrated using the Affymetrix GeneChip data of Cicala et al. The system architecture includes an automated procedure written in Microsoft Visual Basic (VB) 6.0 that updates DAVID weekly with public data from various sources. The data is parsed, formatted, and imported into an Oracle 8i relational database management system (RDBMS). DAVID includes four main modules: Annotation Tool, GoCharts, KeggCharts, and DomainCharts. The Annotation Tool provides several annotation options and builds a tabular view of the users' gene list and the available annotations. GoCharts graphically displays the distribution of differentially expressed genes among functional categories using the controlled vocabulary of the Gene Ontology Consortium (GO). KeggCharts graphically display the distribution of differentially expressed genes among KEGG biochemical pathways. DomainCharts display the distribution of differentially expressed genes among PFAM protein domains. DAVID is compared with related programs such as ENSMART, FatiGO, GeneLynx, GoMiner, MAPPFinder, MatchMiner, Resourcerer, and Source. DAVID combines features of both exploratory tools and annotation tools, providing a comprehensive set of data-mining tools that systematically combine functionally descriptive data with intuitive graphical displays. DAVID's functionality is demonstrated using the Affymetrix GeneChip data of Cicala et al. The tool is designed to facilitate the functional annotation and analysis of any list of genes encoded by human, mouse, rat, or fly genomes. DAVID provides automated solutions that enable researchers to rapidly discover biological themes in large datasets consisting of lists of genes.