What is the proper salutation to address two men in a letter?

The proper salutation to address two men in a letter is "Dear Mr. [Last Name] and Mr. [Last Name]," using their last names. If they have different titles, you should use their respective titles, such as "Dear Dr. [Last Name] and Mr. [Last Name]." If you are unsure of their titles, simply using "Dear [First Name] and [First Name]" is also acceptable for a more informal approach.