Nucleic Acids Research, 2009, Vol. 37, Web Server issue W21 Figure 3. Usage of the ID Converter System on the Web. Input source IDs in the textbox, and select the type of IDs. You may also specify a text-ﬁle with a list of source IDs. Then, select the type of data ID to convert, and push the ‘Search’ button. Then, the system searches for IDs that correspond to source IDs, and shows the list of them. The list can be downloaded by pushing the ‘Download’ button. This ﬁgure shows an example of converting two accession numbers, BC053657 and Z34290, into HUGO Gene Symbols. data IDs on a daily basis, the role of ICS to provide users with the up-to-date information of ID conversion is very important. The usage of the ICS is very simple, and anyone can make full use of it easily. For example, even when one has a list of HUGO gene symbols for 100 genes, he/she can easily ﬁnd corresponding data in H-InvDB, UniProt, PDB and other databases through the ICS. Advantages of the ICS are not limited to this. The most important feature of the ICS is that ID conversion can be done between two types of data IDs that are not directly related. The ICS can convert from and to all data IDs shown in Figure 1, including those that are not directly connected. For example, the ICS can directly convert accession numbers of ISND into PDB IDs. We thus think that the ICS will be a useful Web server for many researchers. We plan to add more and more databases into the HMS and ICS in the future. It is easy to add new data- bases as destination of HMS hyperlinks if the database uses either accession numbers of INSD, UniProt IDs or PDB IDs. We welcome any proposals about incorporat- ing additional databases into the HMS. Furthermore, we have been dealing with databases about human molecular data, but we plan to extend the HMS to molecular data of other species in near future. The ICS will be also extended to incorporate other IDs that are frequently used by biol- ogists. For example, we will incorporate IDs of literature databases, which will enable combining biological knowl- edge in literature with molecular data. We will extend the ICS according to the requests from users. The HMS and ICS will be of considerable use as an automated tool for database managers and as a new