Can anyone please suggest where I could start looking in the code for what might cause orphaned biblioitems? Running the following query: SELECT GROUP_CONCAT('<a target="_blank" href=\"/ cgi-bin/koha/cataloguing/addbiblio.pl?biblionumber=',biblionumber,'\">',biblionumber,'</a>' SEPARATOR ', ') AS BibNums, EXTRACTVALUE(marcxml,'//controlfield[@tag="001"]') AS Id FROM biblioitems GROUP BY Id HAVING count(Id) > 1; finds ~0.1% of our total catalogue with orphans -- often, but not quite always, they are consecutive biblionumbers leading me to think that this happens during cataloguing (but there seems to be no rhyme nor reason as to how it happens, we cannot purposefully duplicate the error.) It's fairly trivial to correct with a " DELETE * FROM biblioitems WHERE biblionumber=123456; " but I'd like to stop it from happening in the first place. Thanks for any suggestions, Paul