Assuming your two lists are in column A of their respective sheets,
highlight all the cells in the master list with A1 as the active cell, and
click on Format | Conditional Formatting, then in the first box choose
Formula Is rather than Cell Value Is. In the Formula box enter this:

=NOT(ISNA(MATCH(A1,Sheet2!A$1:A$300,0)))

(adjusting the sheet name to the one you use). Then click on the Format
button, click on the Patterns tab (for background colour) and choose the
colour you want. Click OK twice to exit the dialogue box.

Hope this helps.

Pete

"JennaB" wrote in message
...
I have a list of about 300 UPC numbers that have been extracted from a
master
list of about 2,000 UPC numbers. These lists are on 2 separate sheets,
and
the 300 UPC numbers are not in a consecutive series. I want to highlight
the
300 UPC numbers within the master list. I don't have time to use the
"find"
function 300 times. Suggestions?