How do I do this?

I have an ID and a Persons name.

I want to show the the names when some selects the drop-list BUT use the related ID stored to the field. I set up the drop-list with the ID then show Lname. I see the Lname in the drop. Whe I make the select I see the ID. how to I still show the Name after it has been selected?

Using 8.5

Read very carefully step 9 here.

Thanks that answers the question. So my drop-list is performing as expected. I don't understand the purpose for makes a menu list display differently then a drop-list.

I guess I need to use a menu list.

Is there a good reason for this design?

I really can't say - it might have something to do with type-ahead being supported in drop-down lists, but not in pop-up menus. Fact is,

"Auto-complete is not supported in drop-down lists when the value list used is configured to use Also display values from second field, Show values only from second field, or Sort by second field."

In any case, you can always go back to the old method of covering the selection field with a display field.