The miRNA Registry is a service that assigns unique names to miRNAs before their publication. It provides a comprehensive and searchable database of published miRNA sequences accessible via a web interface (http://www.sanger.ac.uk/Software/Rfam/mirna/), with all sequence and annotation data freely available for download. Release 2.0 contains 506 miRNA entries from six organisms. MicroRNAs (miRNAs) are non-coding RNA molecules that regulate mRNA translation and degradation. They are transcribed as long primary transcripts (pri-miRNAs), which are processed into hairpin precursor sequences (pre-miRNAs) in the nucleus. The mature miRNA is then excised by Dicer in the cytoplasm. miRNAs are distinguished from other RNA classes like siRNAs based on sequence similarity. The miRNA Registry aims to assign unique names to miRNAs prior to publication and to maintain a comprehensive database of published miRNA sequences. Names are assigned based on sequence similarity, with numerical suffixes for homologous sequences from different organisms. The registry also provides a searchable database with detailed information on each miRNA, including genomic location, homologous sequences, and possible targets. The database is hosted by the Rfam website and is freely available. It includes predicted stem-loop and mature miRNA sequences in FASTA and EMBL formats. The registry ensures long-term curation of miRNA data, allowing for the rationalization of gene names as more data become available. It also integrates with the Rfam database for classification of miRNA sequences into families. The registry encourages feedback and data revisions.The miRNA Registry is a service that assigns unique names to miRNAs before their publication. It provides a comprehensive and searchable database of published miRNA sequences accessible via a web interface (http://www.sanger.ac.uk/Software/Rfam/mirna/), with all sequence and annotation data freely available for download. Release 2.0 contains 506 miRNA entries from six organisms. MicroRNAs (miRNAs) are non-coding RNA molecules that regulate mRNA translation and degradation. They are transcribed as long primary transcripts (pri-miRNAs), which are processed into hairpin precursor sequences (pre-miRNAs) in the nucleus. The mature miRNA is then excised by Dicer in the cytoplasm. miRNAs are distinguished from other RNA classes like siRNAs based on sequence similarity. The miRNA Registry aims to assign unique names to miRNAs prior to publication and to maintain a comprehensive database of published miRNA sequences. Names are assigned based on sequence similarity, with numerical suffixes for homologous sequences from different organisms. The registry also provides a searchable database with detailed information on each miRNA, including genomic location, homologous sequences, and possible targets. The database is hosted by the Rfam website and is freely available. It includes predicted stem-loop and mature miRNA sequences in FASTA and EMBL formats. The registry ensures long-term curation of miRNA data, allowing for the rationalization of gene names as more data become available. It also integrates with the Rfam database for classification of miRNA sequences into families. The registry encourages feedback and data revisions.