The old rules stated that the choice of who or whom must be determined by the grammar of the clause within which this pronoun occurs. Who is the appropriate form for the subject of a sentence or clause: Who is he? He’s the man who wants the key. Whom is the objective form: Whom did he say he was? He’s a man whom I know well.

Those distinctions are rarely observed anymore. Because who or whom frequently occur at the beginning of a sentence or clause, there is a tendency to choose who no matter what the word’s function is. According to Webster’s New Universal Unabridged Dictionary (1996), “Even in edited prose, who occurs at least ten times as often as whom regardless of grammatical function. Only when it directly follows a preposition is whom more likely to occur than who.” This juxtaposition is usually avoided now both in speech and writing, particularly in questions: Who is the letter from? Sometimes it’s avoided by omitting the pronoun altogether: All patients you have had contact with.

The word whom has gone almost completely out of style. And good riddance. Most people use it incorrectly anyway. According to Random House Webster’s Unabridged Dictionary 3.0, “The notion that ‘whom’ is somehow more ‘correct’ or elegant than ‘who’ leads some speakers to hypercorrect uses of ‘whom’: Whom are you? The person whom is in charge of the office has left the building.” That sounds so yesterday.

The new rules seem to indicate that it’s best (and most natural) to use whom only after a preposition: to whom it may concern; to whom are you speaking?

For formal writing, check your dictionary if you aren’t sure when to use whom because there are still sticklers for the “proper” use of this practically archaic word, and it’s best to use it correctly.