NC-IUPHAR (International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification) and its subcommittees provide authoritative reports on the nomenclature and pharmacology of G protein-coupled receptors (GPCRs) that summarize their structure, pharmacology, and roles in physiology and pathology. These reports are published in Pharmacological Reviews (http://www.iuphar.org/nciuphar_arti.html) and through the International Union of Pharmacology (IUPHAR) Receptor Database web site (http://www.iuphar-db.org/iuphar-rd). The essentially complete sequencing of the human genome has allowed the cataloging of all of the human gene sequences potentially encoding GPCRs. The IUPHAR Receptor List (http://www.iuphar-db.org/iuphar-rd/list/index.htm) presents this catalog giving IUPHAR-approved nomenclature (where available), known ligands, and gene names for all of these potential receptors (excluding sensory receptors and pseudogenes) together with links to curated sequence, descriptive information, and additional links in the Entrez Gene database (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=gene). This list is a major new initiative of NC-IUPHAR that, through continuing curation, defines the target of our ongoing receptor classification and invites further input from the scientific community.