For quick diagnostics, think you could also use this:

Assume source data in A2:B2 down
In C2: =IF(A2="","",--ISNUMBER(MATCH(A2,B:B,0)))
In D2: =IF(B2="","",--ISNUMBER(MATCH(B2,A:A,0)))
Copy C2:D2 down to the last row of source data

Col C checks col A against col B
It will return: 0,1 or blanks: "", where
0 = col A value is not found in col B
1 = col A value is found in col B
blanks: "" means there's nothing in col A to be checked

Col D returns similarly for the converse checks of col B against col A

You could then easily apply/use autofilter on cols C & D
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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"Wowbagger" <Wowbagger~~ wrote in message
...
If I have a series of values (serial numbers) derived from one source in
column A and a series of values (also serial numbers) derived from a
second source in column B, is there a way to quickly identify which
numbers do not appear in both columns?