The article describes the TRANSFAC database, which is a comprehensive resource for eukaryotic transcription factors and their DNA binding sites. It provides information on the regulatory sequences and the transcription factors that bind to them, facilitating the understanding of gene expression at the transcriptional level. The database is structured using a relational model, with key tables including SITES, FACTORS, CLASS, and MATRIX, each containing detailed information about regulatory elements, transcription factors, their classifications, and DNA-binding matrices. The SITES table includes details about the location of regulatory sites, the genes they belong to, and the biological species they originate from. The FACTORS table describes the properties of transcription factors, including their biological species, cell-specificities, and structural and functional characteristics. The database also includes information on the quality of DNA-protein interactions, which is determined based on the reliability of experimental data. The database is accessible through ASCII flat files and a web version, and it includes cross-references to other databases such as EMBL, SwissProt, and Flybase. The TRANSFAC database is also connected to the TRRD database, which provides information on regulatory regions at various levels of organization. The article also discusses the development of retrieval tools and database management systems that allow users to access and analyze the data. Future prospects include enhancing cross-referencing between databases, improving access to transcription factor data, and linking the database to more comprehensive sequence analysis programs. The database is freely available and accessible through various online resources.The article describes the TRANSFAC database, which is a comprehensive resource for eukaryotic transcription factors and their DNA binding sites. It provides information on the regulatory sequences and the transcription factors that bind to them, facilitating the understanding of gene expression at the transcriptional level. The database is structured using a relational model, with key tables including SITES, FACTORS, CLASS, and MATRIX, each containing detailed information about regulatory elements, transcription factors, their classifications, and DNA-binding matrices. The SITES table includes details about the location of regulatory sites, the genes they belong to, and the biological species they originate from. The FACTORS table describes the properties of transcription factors, including their biological species, cell-specificities, and structural and functional characteristics. The database also includes information on the quality of DNA-protein interactions, which is determined based on the reliability of experimental data. The database is accessible through ASCII flat files and a web version, and it includes cross-references to other databases such as EMBL, SwissProt, and Flybase. The TRANSFAC database is also connected to the TRRD database, which provides information on regulatory regions at various levels of organization. The article also discusses the development of retrieval tools and database management systems that allow users to access and analyze the data. Future prospects include enhancing cross-referencing between databases, improving access to transcription factor data, and linking the database to more comprehensive sequence analysis programs. The database is freely available and accessible through various online resources.