Personally, I wish Microsoft would allow us to define ImportSpecifications
for Excel files, like they do for csv, text, ...  Unfortunately, they have
decided that they can figiure out what our Excel data is supposed to look
like better than we can.

Have you tried linking to the spreadsheet rather than importing?  This will
prevent bloating of your database, and the need to compact occassionally.

I've found that if the import wizard decides that a field is of one
datatype, and the actual data in that row for one of the records doesn't
match the datatype, that Access will drop rows, but as Jerry mentioned, this
usually results in an ???_ImportErrors table.  This is another reason for
creating a table, defining its structure to match what the import datashould
be (make sure to allow Null values if you have some fields that contain
Nulls), and then import the data into that table, rather than creating the
table during the import.

HTH
Dale