There are a couple of good, free tools for cleaning up duplicate contacts.
See http://www.slipstick.com/addins/contacts.htm#dupe

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Sue Mosher, Outlook MVP
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> Despite the filter that is intended to prevent this, I have many duplicate
> contacts in my contact list. Is there a way to merge the email and
> address
> information into only one record or do all duplicates need to be manually
> deleted