Just curious which one should be good deploy first. We currently have exchange 2007 with OCS 2007.

It does not matter because ocs/lync client plug in to Outlook. As for upgrading either Exchange 2010 or Lync 2010 it does not matter.

Agree, it doesn't matter at all. Cheers,Gulab | MCITP: Exchange 2010-2007 | Skype: Gulab.Mallah | Blog: www.ExchangeRanger.blogspot.com

As I know, you need to aware the information below for upgrade Lync 2010 Compatibility If the version of OCS is just 2007 instead of 2007 R2, please also check out my post in the thread below Office Communicator 2005 functionality in an Exchange 2010 SP1 Environment Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.