The Nucleic Acids Research online Molecular Biology Database Collection is a public repository that lists more than 1000 databases described in this and previous Nucleic Acids Research annual database issues, as well as a selection of molecular biology databases described in other journals. All databases included in this Collection are freely available to the public. The 2008 update includes 1078 databases, 110 more than the previous one. The links to more than 80 databases have been updated and 25 obsolete databases have been removed from the list. The complete database list and summaries are available online at the Nucleic Acids Research web site, http://nar.oxfordjournals.org/.