Invite ?

I believe it's Dr. Jane Smith and Dr. John Doe

Not Dr. Jane Smith and John Doe

Nor, Mr. and Mrs.

This is what I found.

When both husband and wife are identically degreed, use Drs. John and Jane Doe or The Doctors Doe. In the case of a married couple and the wife is a doctor the title should read Dr. Jane Doe and Mr. John Doe. If the husband is the doctor, the correct title would be Dr. and Mrs. John Doe.

Ok, I was right, you can also try these other two:

The Doctors Stevenson, Dr. Carmen Stevenson and Dr. Andrew Stevenson, Drs. Carmen and Andrew Stevenson.

source:
http://www.weddingchannel.com/ui/buildArticle.action?assetUID=2809

oops. i addressed one as Dr & Dr. Joe Shmo.

oh well.... do people really look at the envelope anyway??