Thank you for getting back to me. One thing I should have mentioned earlier is that, the list I would like to retain (worksheet 1) contains about 23,000 different anti-viral agents. The rest of the anti-viral agents have to be deleted from the bigger list containing roughly 30,000 anti-viral agents(Worksheet 2). List 2 contains the anti-viral agents from list 1 but it contains 7,000 additional anti-viral agents that I wont be needing. Hope the question is clear.