ISfinder (www-is.biotoul.fr) is a dedicated database for bacterial insertion sequences (ISs), serving as a reference center for ISs and providing a coherent nomenclature system. It was established to replace the Stanford reference center and includes extensive background information on ISs and transposons. The database is divided into several sections, including general information, specific IS families, and nomenclature guidelines. Users can request names for new ISs and submit sequences for deposition, which helps maintain an accurate and up-to-date resource. ISfinder also offers an online Blast facility and plans to add additional features like alignment capability, PsiBLAST, and HMM profiles. The database is used for annotating bacterial genomes and is recommended by several microbiology journals for registering new IS elements before publication. It aims to interact with other specialized databases and continues to provide insights into the phylogenetic distribution and influence of ISs on genome structure.ISfinder (www-is.biotoul.fr) is a dedicated database for bacterial insertion sequences (ISs), serving as a reference center for ISs and providing a coherent nomenclature system. It was established to replace the Stanford reference center and includes extensive background information on ISs and transposons. The database is divided into several sections, including general information, specific IS families, and nomenclature guidelines. Users can request names for new ISs and submit sequences for deposition, which helps maintain an accurate and up-to-date resource. ISfinder also offers an online Blast facility and plans to add additional features like alignment capability, PsiBLAST, and HMM profiles. The database is used for annotating bacterial genomes and is recommended by several microbiology journals for registering new IS elements before publication. It aims to interact with other specialized databases and continues to provide insights into the phylogenetic distribution and influence of ISs on genome structure.