A polite/respectful way to ask who someone is (e.g. on the phone). Used when asking a person's identity in honorific speech.
電話に出て『どちら様ですか』と訊ねた。
I answered the phone and asked, 'Who is this, please?'
訪問先でインターホン越しに『どちら様ですか』と聞かれた。
At the door the intercom asked, 'Who is it, please?'