What is the proper salutation for letter to husband and wife both attorneys?

The proper salutation for a letter addressed to a husband and wife who are both attorneys would be "Dear Mr. and Mrs. [Last Name]" or "Dear [First Name] and [First Name] [Last Name]." If you want to acknowledge their professional titles, you could use "Dear Attorneys [Last Name]." This conveys both respect for their professional status and addresses them as a couple.