One way, in D1:
=NOT(ISERROR(VLOOKUP(A1,$B$1:$B$1000,1,FALSE)))
Fill down to D15000

HTH. Best wishes Harald

"BPR" skrev i melding
...
I have two colums: A and B, both containing text. In A I have 15000 rows,
in
B I have 1000 rows. I need to identify the rows where values in A also are
in
B. How can I do this?