A complete list of known and putative E.coli cytoplasmic membrane transporters has previously been compiled, and each of these transporters was classified on the basis of amino acid sequence similarities and transport function (5) (see also http://www-biology.ucsd.edu/~ipaulsen/transport/ and http://www-biology.ucsd.edu/~msaier/transport/ ). This compilation of over 300 transporters was imported into EcoCyc, and each transporter is now being annotated using the same detailed, literature-based approach that EcoCyc uses for E.coli enzymes and pathways. For each transporter, a comprehensive literature search of MEDLINE and Current Contents is performed for relevant keywords. Citations in relevant journal papers are used to identify further pertinent articles. Additionally, the background knowledge of transport systems of the two transport editors proved invaluable, and in some instances experts working on particular transport systems are contacted to clarify their findings.