It seems like Access can only show (and work with) the
first 65536 records in a combo box drop-down list. Is
there any way of tracking down the variable Access uses
to store this number - is it perhaps 32-bit in later
versions?

I'm using Access 97 although the problem persists after
conversion in Access 2000. The "listcount" property
reports 65535 records, but the query I'm using as
the "rowsource" returns over 200000 results when run BY
itself.

65536 is a very generous limit for a combo box.  How many days do you want
your user to scroll down it?  I think that you need to think of some way to
limit the number of items in the box.  Have the user select the first
character of the alphabet or first few letters or numbers or some other
limitation.  Then only fill the combo box with the limited items.  HTH

Kim