Provides a biological trace elements database. dbTEU includes all known transporters and user proteins (excluding metal-binding chaperones and regulators) for five trace elements: Cu, Mo, Ni, Co and Se, in more than 700 sequenced organisms across the three domains of life. Approximately 16 500 proteins are stored in the database. In addition, this resource offers multiple search and browse options, such as BLAST homology searches. It also allows compilation of sets of trace element utilization proteins in individual organisms.