I have two columns in excel, and I want to find (preferably highlight) the items that are in column B, but not in column A.
What's the quickest way to do this?
I have two columns in excel, and I want to find (preferably highlight) the items that are in column B, but not in column A. What's the quickest way to do this? 


If the formula fails to find a match, it will be marked #N/A, otherwise it will be a number. If you'd like it to be TRUE for match and FALSE for no match, use this formula instead:
If you'd like to return the unfound value and return empty string for found values



Here's a quickanddirty method. Highlight Column B and open Conditional Formatting. Pick Use a formula to determine which cells to highlight. Enter the following formula then set your preferred format. =countif(A:A,B1)=0 


Took me forever to figure this out but it's very simple. Assuming data begins in A2 and B2 (for headers) enter this formula in C2:
Then click and drag down. A cell with Please note that you need to change $A$287 to match your entire search array in Column A. For instance if your data in column A goes down for 1000 entries it should be $A$1000. 


See my array formula answer to listing A not found in B here:



My requirements was not to highlight but to show all values except that are duplicates amongst 2 columns. I took help of @brenton's solution and further improved to show the values so that I can use the data directly:
Copy this in the first cell of the 3rd column and apply the formula through out the column so that it will list all items from column B there are not listed in column A. 


Thank you to those who have shared their answers. Because of your solutions, I was able to make my way to my own. In my version of this question, I had two columns to compare  a full graduating class (Col A) and a subset of that graduating class (Col B). I wanted to be able to highlight in the full graduating class those students who were members of the subset. I put the following formula into a third column:
This coded most of my students, though it yielded some errors in the first few rows of data. 


There is an error in the formula above =IF(ISNA(MATCH(B2,$A$2:$A$2642,0)), A2, "") should be =IF(ISNA(MATCH(B2,$A$2:$A$2642,0)), B2, "") 


in 

