Hello, I will do what I can to try to answer your question. I am not sure what you mean specifically by book information, but here is, to the best of my knowledge, how Koha store the book info. in the database. There are three major tables that hold book information: biblio: This table holds the information about "works" such as the author, title, and copyright date. biblioitems: This table holds the information about various "manifestations" of works. These would be things such as an ISBN number, year of publication, number of pages, etc. Each biblioitem corresponds to one of the entries in the biblio table. items: This table contains information about an item (an actual physical copy of a biblio/biblioitem). These are things such as price, barcode, branch, date last borrowed, etc. Now, it is when we get to the MARC stuff that I start getting a little uncomfortable (so Paul, if I say anything that is wrong, please correct me. Thanks). In the marc_subfield_structure table are all of the subfields for various MARC tags. There is a column for each of the subfields (kohafield) which serves as a link between the rows of biblio, biblioitems, and items and the MARC records. The various functions that are deal with this process are found in C4/Biblio.pm. I hope this helps you out a bit. Mike -- Mike Hansen <mwhansen@hmc.edu>