I asked Mendeley support and their (not very helpful) reply was as follows: "Unfortunately EndNote does not export group structures from the program. The best thing to do in this situation would be to tag documents with the group name and then use the Filter By Tags view in Mendeley Desktop to recreate groups in the program. Apologies for any inconvenience this may cause you". I think by 'tag' this means add some distinguishing word to some field like the Label field of all references in each EndNote group. There might be some simpler method to separately export each group from EndNote into a Mendeley group.

Hi, with Endnote X6 i just discovered how to do this.

In Endnote:

1. Go to your 'Group'- select all entries within the group (click on the first entry, hold shift, click on the last entry)

2. 'Tools' -> 'Change/move/copy fields'

3. In 'Change fields' - select 'labels' from the drop down list

4. Select 'insert after'

5. type in your Groups name

6. All your entries will now be 'tagged' with your Groups name & will show up as 'tags' in Mendeley

You can also do this to add keywords to your Endnote libraries

Thanks Patrick...this is deal breaker for me- no way I am going through hundreds of references to do this!