An AutoFilter dropdown list will only show 1000 entries. If your column
has more than 1000 unique items, they can be filtered, but they can't
all be displayed in the dropdown list. The items in the column appear
alphabetically sorted in the dropdown list, and only the first 1000
alphabetical entries will appear.

To AutoFilter for an item that doesn't appear in the dropdown list, you
can choose Custom from the dropdown list, and type the criteria, as
you're currently doing. Also, there are a couple of workarounds he

http://www.contextures.com/xlautofilter02.html


Janice Lee via OfficeKB.com wrote:
I have a query with 6058 rows of IDs.
When I sort them in ascending order, it goes from 1001 to 2083440.
However, when I select all and put a filter, the filter only goes down to
3147. Why is that? When I look at the entire worksheet, the IDs greater
than 3147 are still there.
Please help as I need this for work!
Thanks!



--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html