I'm using a self referencing HABTM model with Participants. You sign up for an event and when you log in to your reservation/profile you see a list of other participants and you can choose to add yourself and others into various groups; share hotel room, share transportation from airport etc. What I've managed so far: 1) In my profile I see the list of all other participants with checkboxes. Great so far. 2) Adding another participant works fine. Next time I edit, the participant I added is shown as checked. 3) Removing another participant works fine too as long as you still have checked participants before you submit! Again, with words: There are 3 participants. I'm logged in as one of them, and I see the 2 other people on the participants list. I choose to check both of them. This works fine (always). Later I choose to remove one of them (by unchecking the checkbox and hitting submit). This also works fine (always). If I want to remove the last checkbox... nothing is updated (always!). What's curious is that I can add and remove any odd combination of participants and it will always work UNLESS I choose to remove every participants in one go (removing a one and only participant is a special case of "remove all checked participants"). As far as I know, HABTMs work by first deleting all relations, then re-saving them. I can see that in my tables when I remove, add, remove, add the same participant over and over again - the id on the HABTM table is always increasing. When I deselect all participants at once, however, the relations are not updated. The ids stay the same, so it's like the save never happened. This behaviour is so specific and peculiar, I have a feeling I'm missing something obvious here. Anyway, here's the relevant code: Model class Participant extends AppModel { var $hasAndBelongsToMany = array( 'buddy' = array( 'className' = 'Participant', 'joinTable' = 'participants_participants', 'foreignKey' = 'participant_id', 'associationForeignKey' = 'buddy_id', 'unique' = true, ) ); Controller function edit($id = null) { if (!$id && empty($this-data)) { $this-Session-setFlash(__('Invalid Participant', true)); $this-redirect(array('action'='index')); } if (!empty($this-data)) { if ($this-Participant-saveAll($this-data)) { $this-Session-setFlash(__('The Participant has been saved', true)); $this-redirect(array('action'='index')); } else { $this-Session-setFlash(__('The Participant could not be saved. Please, try again.', true)); } } if (empty($this-data)) { $this-data = $this-Participant-read(null, $id); } // Fetching all participants except yourself $allParticipants = $this-Participant-find('list', array('conditions' = array('participant.id ' = $id))); // Fetching every participant that has added you to their list $allBuddies = $this-Participant-ParticipantsParticipant-find('list', array( 'conditions' = array('buddy_id' = $id), 'fields' = 'ParticipantsParticipant.participant_id', 'order' = 'ParticipantsParticipant.participant_id ASC' )); $this-set(compact('allParticipants','allBuddies')); } View echo $form-create('Participant'); echo $associations-habtmCheckBoxes($allParticipants, $this-data['buddy'], 'buddy', 'div', '\'border: 1px solid #000;\'', '\'border: 1px solid #000;\''); echo $form-end('Submit'); I'm using a slightly modified helper, habtmCheckBoxes, found here: http://cakeforge.org/snippet/detail.php?type=snippet&id=190 It works like this: function habtmCheckBoxes($rows=array(), $selectedArr=array(), $modelName, $wrapTag='p', $checkedDiv, $uncheckedDiv) {}