The WHO Nomenclature Committee for Factors of the HLA System met following the 14th and 15th International HLA and Immunogenetics Workshops to document additions and revisions to the nomenclature of HLA specificities. The report covers naming conventions for HLA genes and alleles, conditions for accepting new allele sequences, serological specificities associated with alleles, the introduction of colon-delimited HLA allele names, reporting of ambiguous HLA allele typing, and gene and protein nomenclature. The IMGT/HLA Sequence Database serves as the official repository for HLA sequences and provides tools for their retrieval and analysis. The committee also discusses the use of standard genetic nomenclature for HLA allele sequences at the gene and protein levels. The report includes a list of committee members involved in preparing the document.The WHO Nomenclature Committee for Factors of the HLA System met following the 14th and 15th International HLA and Immunogenetics Workshops to document additions and revisions to the nomenclature of HLA specificities. The report covers naming conventions for HLA genes and alleles, conditions for accepting new allele sequences, serological specificities associated with alleles, the introduction of colon-delimited HLA allele names, reporting of ambiguous HLA allele typing, and gene and protein nomenclature. The IMGT/HLA Sequence Database serves as the official repository for HLA sequences and provides tools for their retrieval and analysis. The committee also discusses the use of standard genetic nomenclature for HLA allele sequences at the gene and protein levels. The report includes a list of committee members involved in preparing the document.