have the following models class Address < ActiveRecord::Base has_and_belongs_to_many :address_types, :join_table => "address_types_addresses", :foreign_key => "address_id" has_and_belongs_to_many :organisations class AddressType < ActiveRecord::Base has_and_belongs_to_many :addresses, :join_table => "address_types_addresses", :foreign_key => "address_types_id" class Organisation < ActiveRecord::Base has_and_belongs_to_many :addresses An organisation can have a number of different addresses (main, dispatch, invoice etc). And one address can belong to more than one organisation (to allow for different companies operating out of the same address), and an address can be more than one type of address (ie the invoice address could be the same as the dispatch address, but different to the main office address). There are the appropriate join tables: address_types_addresses, and addresses_organisations. I have a form that allows a user to add a new address (uses Ryan Bates'' "Handle Multiple Models in One Form" technique from the Advanced Rails Recipes book. Here is the relevant part of the Organisations model: after_update :save_addresses def new_address_attributes=(address_attributes) #handles the address edit form in the edit view address_attributes.each do |attributes| addresses.build(attributes) end end def existing_address_attributes=(address_attributes) addresses.reject(&:new_record?).each do |address| attributes = address_attributes[address.id.to_s] if attributes address.attributes = attributes else addresses.delete(address) end end end def save_addresses addresses.each do |address| address.save(false) end end The problem I am having is that the save is great - except for it doesn''t enter a value in the address_types_address table. Being an old-fashioned PHP programmer, I am slightly struggling to find out how to make it update that table as well. I am guessing that since there is no direct relationship between address_types and organisations, rails doesn''t know about it. How to tell it .... Is this something simple, or is there a bus-sized hole in the logic? Any help would be v gratefully received. Thanks Ben