The information on protein molecule structure at atomic resolution is useful for various purposes such as understanding the mechanism of chemical reaction and developing medicines for therapy. We manage Protein Data Bank (PDB), the archive of such data. We receive the deposition of structural data determined by experimental method, and provide the archive which is accessible with no charge. PDB was established in 1971 with seven structures. Recently the number of entries increased dramatically by developing the experimental method and now we keep more than 100,000 PDB entries. PDB includes various structures such as myoglobin (PDB entry 1mbn (Figure 1), which is the first structure of the protein) and hemoglobin, which is composed of four myoglobin-like chains. We also provide interactive interface "Yorodumi"(Figure 2), which enables the operation of molecules by mouse action. Another feature of our site is a Japanese keyword search (Figure 3).