How should I address holiday greetings to business associates?

Q. How do you formally address Christmas cards being sent to clients and business associates? What is the proper way to address people such as doctors and their spouses, attorneys and their spouses, and when a married couple has different last names? I'm sure there are others but I can't think of them right now.

L.F., Tucson

A. Holiday season is clearly upon us. Recently I have received letters like this one asking how to address business cards and correspondence, so here's a breakdown of the different combinations and ways to address business mail this holiday season.

The most basic way to address a married couple with the same last name is "Mr. and Mrs. David Jones." A more informal and acceptable alternative is "Alice and David Jones" or "David and Alice Jones." Today, either name can be first.

If the people have different last names but are living together as a couple, then the address would be "Alice Smith and David Jones" or "Ms. (not Mrs.) Alice Smith and Mr. David Jones" all on one line. If two people are living together but aren't a couple, then you would write (Ms.) Alice Smith on the first line and then (Mr.) David Jones on the second line. The titles are optional.

In business correspondence if you're sending to a married woman, use Ms. rather than Mrs. Either "Ms. Nancy Smith" or the more informal "Nancy Smith" is correct.

When writing a business communication to a lawyer, you can use the suffix Esq. or Esquire. If you use the suffix, do not also use the title Mr. or Ms. A lawyer is addressed either as "Mr. David Jones" or "David Jones, Esq." When writing to a lawyer and spouse the title is dropped: "Mr. and Mrs. David Jones."

Medical doctors use their title both in business and social communications. The rule of thumb when addressing people who have earned a title such as Doctor or Reverend or a military title such as Captain or General, is that person's name comes first, a professional title comes before a social title. If the woman uses her husband's name socially, the address is "Dr. Barbara and Mr. James Werner." If she uses her maiden name both professionally and socially, it's "Dr. Barbara Hanson and Mr. James Werner." Note that her name comes first because her professional title "outranks" his social title. If both husband and wife are doctors and they use the same last name, the address is either "The Drs. Werner" or "Drs. Barbara and James Werner" either first name can go first. Either of these two options is used whenever both people have the same title.

Peter Post is the great-grandson of manners guru Emily Post and is the director of the Emily Post Institute in Burlington, Vt.

NEED ADVICE? E-mail questions about business etiquette to bizmanners@globe.com; fax to 617-929-3183; or mail to Etiquette at Work, The Boston Globe, P.O. Box 55819, Boston, MA 02205-5819.