The National Center for Biotechnology Information (NCBI) provides a comprehensive suite of online resources for biological information and data, including the GenBank nucleic acid sequence database and the PubMed database of citations and abstracts. Additional resources focus on literature, medical genetics, genes and genomics, proteins, and chemicals. The Entrez system facilitates search and retrieval operations across these databases, and custom implementations of the BLAST program are available for specialized data sets. Recent developments include new tools such as the Variation Viewer for displaying human variations, PubMed Commons for sharing information on scientific publications, and updates to resources like ClinVar, GTR, and MedGen. NCBI also offers enhanced features for the Gene and Protein databases, and improvements to the taxonomy, genome, and protein databases. The NCBI Guide serves as an interactive directory, and the Entrez system supports text searching, data downloading, and linking between databases. NCBI receives data from direct submissions, collaborations, and internal curation efforts, and provides detailed documentation and support through various resources.The National Center for Biotechnology Information (NCBI) provides a comprehensive suite of online resources for biological information and data, including the GenBank nucleic acid sequence database and the PubMed database of citations and abstracts. Additional resources focus on literature, medical genetics, genes and genomics, proteins, and chemicals. The Entrez system facilitates search and retrieval operations across these databases, and custom implementations of the BLAST program are available for specialized data sets. Recent developments include new tools such as the Variation Viewer for displaying human variations, PubMed Commons for sharing information on scientific publications, and updates to resources like ClinVar, GTR, and MedGen. NCBI also offers enhanced features for the Gene and Protein databases, and improvements to the taxonomy, genome, and protein databases. The NCBI Guide serves as an interactive directory, and the Entrez system supports text searching, data downloading, and linking between databases. NCBI receives data from direct submissions, collaborations, and internal curation efforts, and provides detailed documentation and support through various resources.