The IPD-IMGT/HLA Database is a comprehensive resource for the human Major Histocompatibility Complex (MHC) gene sequences, containing over 25,000 alleles for 45 genes. This database, hosted at http://www.ebi.ac.uk/ipd/imgt/ha, provides a stable, accessible, and user-friendly repository for HLA allele sequences, which are critical for successful transplantation. The MHC region is the most polymorphic in the human genome, with some genes being hyperpolymorphic, containing thousands of variants. The database has evolved over the past two decades, incorporating new technologies and data sources to manage the increasing number of submissions and the complexity of sequences. The database now includes over 24,000 HLA alleles, with more than 362,709 distinct nucleotide variants compared to the reference sequence. The IPD-IMGT/HLA Database offers a range of tools for HLA sequence analysis, including sequence alignments, allele queries, sequence search tools, cell queries, and downloads. These tools are either custom developed or integrated with existing resources from the European Molecular Biology Laboratory. The database receives submissions from over 46 countries and has processed more than 53,410 submissions since its launch in 1998. The database is the official repository for the WHO Nomenclature Committee for Factors of the HLA System and provides official allele designations. The database is updated every three months and includes a variety of data formats, such as FASTA, PIR, and MSF. The database has faced challenges due to the development of new sequencing technologies, which have increased the accuracy and coverage of full-gene sequences. This has led to an increase in the number of full-length gene sequences for class I genes compared to partial sequences. The database must continue to curate and provide tools for the analysis of these complex sequences. The database also needs to support the growing number of submissions and the increasing complexity of sequences, which requires new methods and technologies. The database plays a crucial role in the study of HLA polymorphism and its implications for immune response and disease. It is essential for both clinical and genomic research, providing a comprehensive resource for the study of HLA variation.The IPD-IMGT/HLA Database is a comprehensive resource for the human Major Histocompatibility Complex (MHC) gene sequences, containing over 25,000 alleles for 45 genes. This database, hosted at http://www.ebi.ac.uk/ipd/imgt/ha, provides a stable, accessible, and user-friendly repository for HLA allele sequences, which are critical for successful transplantation. The MHC region is the most polymorphic in the human genome, with some genes being hyperpolymorphic, containing thousands of variants. The database has evolved over the past two decades, incorporating new technologies and data sources to manage the increasing number of submissions and the complexity of sequences. The database now includes over 24,000 HLA alleles, with more than 362,709 distinct nucleotide variants compared to the reference sequence. The IPD-IMGT/HLA Database offers a range of tools for HLA sequence analysis, including sequence alignments, allele queries, sequence search tools, cell queries, and downloads. These tools are either custom developed or integrated with existing resources from the European Molecular Biology Laboratory. The database receives submissions from over 46 countries and has processed more than 53,410 submissions since its launch in 1998. The database is the official repository for the WHO Nomenclature Committee for Factors of the HLA System and provides official allele designations. The database is updated every three months and includes a variety of data formats, such as FASTA, PIR, and MSF. The database has faced challenges due to the development of new sequencing technologies, which have increased the accuracy and coverage of full-gene sequences. This has led to an increase in the number of full-length gene sequences for class I genes compared to partial sequences. The database must continue to curate and provide tools for the analysis of these complex sequences. The database also needs to support the growing number of submissions and the increasing complexity of sequences, which requires new methods and technologies. The database plays a crucial role in the study of HLA polymorphism and its implications for immune response and disease. It is essential for both clinical and genomic research, providing a comprehensive resource for the study of HLA variation.