It depends how you are checking for duplicates. The formula you are using
would have been useful. Assuming you are using a formula like:
=a1=a2
This will check the entire cell contents, including any spaces or
unprintable characters which may not display.

When you use ctrl-f, you're checking the cell to see if it contains the
string you entered. Trailing spaces, for example, would be ignored.

You can try using the Trim function, as in:
=trim(a1)=trim(a2)
That may solve your problem. If not, you'll need to go searching for
extraneous undisplayed characters.

Regards,
Fred.

"boombox" wrote in message
...
I have a giant list of emails that I need to clean up, and I'd like to do
it
by highlighing the duplicates. I use the conditional formatting tool, and
it
only works for some. I can clearly see duplicates that it isn't
highlighting, though it will for others. It is just text, not merged or
hyperlinked or formatted any different. For the duplicates it doesn't
highlight, I can copy one dup and "find" (ctrl + f) the other. If it can
"find" both duplicates, and it will highlight others, why doesn't it work
consistently??