The Publisher Item Identifier (PII) is a unique identifier used by a number of scientific journal publishers to identify documents.^[1] It uses the pre-existing ISSN or ISBN of the publication in question, and adds a character for source publication type, an item number, and a check digit.

The system was adopted in 1996 by the American Chemical Society, the American Institute of Physics, the American Physical Society, Elsevier Science, and the IEEE.

A PII (pii) is a 17-character string, consisting of:

• one character to indicate source publication type: "S" = serial with ISSN, "B" = book with ISBN
• ISSN (8 digits) or ISBN (10 characters) of the serial or book to which the publication item is primarily assigned
• in the case of serials an additional two digit number to pad the difference between the 8-digit ISSN and an ISBN (suggested are the last two digits of calendar year of the date of assignment, which is not necessarily identical to the cover date)
• a 5-digit number assigned by the publisher that is unique to the publication item within the serial or book
• a check digit (0-9 or X)

When a PII is printed (as opposed to stored in a database), the 17-character string may be extended with punctuation characters to make it more readable to humans, as in Sxxxx-xxxx(yy)iiiii-d or Bx-xxx-xxxxx-x/iiiii-d.

• Buscemi, Lara; Ramonet, David; Klingberg, Franco; Formey, Aurélie; Smith-Clerc, Josiane; Meister, Jean-Jacques; Hinz, Boris (2011). "The Single-Molecule Mechanics of the Latent TGF-β1 Complex". Current Biology. 21 (24): 2046–2054. Bibcode:2011CBio...21.2046B. doi:10.1016/j.cub.2011.11.037. ISSN 0960-9822. PMID 22169532. PII S0960-9822(11)01319-4.

• Serial Item and Contribution Identifier (SICI)
• Digital Object Identifier (DOI)
• OpenURL
• Template:PII

• Norman Paskin (September 1996). "Document identifiers: an update on current activities". Quarterly Newsletter of the International Council for Scientific and Technical Information (23). Archived from the original on 2002-11-18.