can you de dupe using any fields other than email?

I think it's just by email. Because Marketo uses email address as the primary ID and syncs with SFDC (or whatever CRM you have) this way, I never put leads into our database without email addresses.

You could manually try de-duping or supplementing data or mabye do this through something like SFDC Data Loader?

Thanks Kim.  Very helpful!

You could always create a smart list in the lead database that filters based on the items you want to inspect for duplicates. From there, you could sort by that item (unless it is a custom field), and easily spot duplicates to eliminate. The process would be manual and possibly easier to do through your CRM, but that depends on how many duplicates you identify.

You can also check for Last Name or Full Name matches by using the Duplicate Fields filter. If you check the smart list portion of the Possible Duplicates smart list in the System Smart Lists folder.

Thanks Everyone.  I will try these work arounds.