The Molecular Biology Database Collection: 2004 update.

The Molecular Biology Database Collection is a public resource listing key databases of value to the biologist, including those featured in this issue of Nucleic Acids Research, and other high-quality databases. All databases included in this Collection are freely available to the public. This listing aims to serve as a convenient starting point for searching the web for reliable information on various aspects of molecular biology, biochemistry and genetics. This year's update includes 548 databases, 162 more than the previous one. The databases are organized in a hierarchical classification that should simplify finding the right database for each given task. Each database in the list comes with a recently updated brief description. The database list and the database descriptions can be accessed online at the Nucleic Acids Research web site http://nar. oupjournals.org/.