VKCDB is a comprehensive sequence database of voltage-gated potassium channels (VKCs) from Eukaryotes, Bacteria and Archaea, designed to serve as a resource for research on VKC evolution and structure/function relationships. Protein sequences, corresponding nucleic acid sequences of open reading frames, references, information on the organisms of origin of each channel and functional data are stored in this database. The current version (v 2) has been significantly expanded and updated since the release of v1 in 2003.