Edmund, This smells like the otehr side of the weird behaviour I was experiencing. You haven't got any FieldIndexes in there, one of which may have some empty strings indexde in it? Anyway, Try applying the patch in this message I posted to zope-dev this morning "ZCatalog FieldIndex Bug (Fix?)" ...and let me know if it helps (or if it breaks everything ;-) cheers, Chris (!M) ;-)