The Australian ISBN Agency is operated by Thorpe-Bowker.

The International Standard Book Number (ISBN) is a 13-digit number that uniquely identifies books and book-like products published internationally. While an ISBN is not mandatory, and does not provide copyright on a work, it is the principal world-wide ordering device for the international book trade and library market.

Publishers who wish to apply for an ISBN should contact ISBN Agency Australia at the following address:

ISBN Agency
Level One, 607 St Kilda Road 
(PO Box 6509, St Kilda Road Central VIC 8008)
Melbourne Vic, 3004

Tel: +61 3 8517 8349
Fax: +61 3 8517 8368

Further information is available at Thorpe-Bowker's My Identifiers homepage.