For my current project, I need to implement both one-to-many and many-to-many bidirectional indexed associations. (For the many-to-many assoc, one end is indexed but the other is not.) As stated in section "6.8. Bidirectional Associations" of the documentation, "NHibernate does not support bidirectional one-to-many [or many-to-many] associations with an indexed collection (list, map or array) as the 'many' end". A work-around for the one-to-many case is posted here: http://www.hibernate.org/193.html. Does anyone know of a similar work-around for the many-to-many case? I'm worried there won't be one as straight-forward as the former. Ideally NHibernate would add support for such associations. I've found messages in the forum discussing this problem which have been posted as far back as May 2005. From what Sergey wrote in May of this year here (http://forum.hibernate.org/viewtopic.php?t=974301#2351927) it sounded like somewhat of a priority. So I'm wondering if perhaps this has already been fixed but not documented? If it hasn't yet been fixed then I encourage those interested to please vote for it: http://jira.nhibernate.org/browse/NH-298.