My brain is a little fried so I need some help.

I have 2 sets of users - let's call them User set A and User set B.

User set A needs to have 5 Extra Fields assigned to them.

User set B has the same 5 Extra Fields as user set A but user set B gets an additional 2 Extra Fields.

So I can set up the 2 sets of Extra Fields for both user groups. Not a problem.

But how do I associate a User Group with an Extra Fields Group so that each user group is only presented with the appropriate set of extra fields?

Extra fields are associated with k2 categories and not users. You can only assign one extra field group to a category, but you can associate the same extra field group with more that one category

Thanks William. Can you point me to a resource that will show me how to associate an Extra Field Group to more than one category?

Create and extra field group
Create the fields and assign them to the group
Open the category settings
Select the Extra field group
Open the other category
do the same

Thanks William. That makes sense, but doesn't quite get me where I need to be.

Can you offer any advice about how to deal with 2 user groups that have similar, but slightly different fields? See my first post.

Again, the extra fields belong to extra field groups, and the extra field groups are associated with k2 categories, not k2 user groups

I understand what you are saying about the association. So should I assume that I what I want to do isn't possible with K2?