programs called Entrez Utilities (http://www.ncbi.nlm .nih.gov/books/NBK25501/). CONCLUSIONS AND FUTURE DEVELOPMENTS As the capacity and complexity of biological data sets expands, databases face new challenges in ensuring that the information is adequately organized and described. The NCBI BioProject and BioSample databases are being developed to help address these challenges by providing the means by which data generators can organize and describe a broad range of study designs and sample types, and link to corresponding sets of experimental data in archival databases. Archival databases must rely heavily on submitters to provide appropriate annotations and context for their projects and samples. The aim of the NCBI Submission Portal is to provide an intuitive interface that balances the requirement for straightforward data input, while encouraging provision of rich and consistent metadata across multiple archival databases and data types. There is a growing appreciation in the community that metadata, in addition to the actual data itself, is essential for interpreting experimental results, for example, when attempting to ascribe function and process to genes, or correlating data with phenotype information. Improved metadata and increased sharing of terminologies across databases provide greater opportunities for data aggrega- tion and making the scientiﬁc connections that help trans- form data into knowledge. Development of these databases and the Submission Portal is on-going. Many technical reﬁnements are cur- rently being worked on including expanding integration and linking with other databases at NCBI, EBI and DDBJ, improving visualization of object relationships and hierarchies, extending support for controlled vocabularies and checklists for speciﬁc BioSample types, enabling batch submission of multi-part projects, building curatorial interfaces, enhancing BioProject web summaries and implementing special reports for funding agencies. ACKNOWLEDGEMENTS The authors thank our EBI colleagues including Alvis Brazma, Helen Parkinson and Ewan Birney for valuable discussions. We also wish to thank the many NCBI staff members who have contributed to discussions and provided data or feedback on these resources, in particu- lar, Mike Feolo, Martin Shumway, Anjanette Johnston, Christopher O’Sullivan, William Klimke, Vasuki Palanigobu, Reza Safarnejad and Anatoly Mnev. 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