This paper proposes a way to improve the translation quality by using information on dialogue participants that is easily obtained from outside the translation component. We incorporated information on participants' social roles and genders into transfer rules and dictionary entries. An experiment with 23 unseen dialogues demonstrated a recall of 65% and a precision of 86%. These results showed that our simple and easy-to-implement method is effective, and is a key technology enabling smooth conversation with a dialogue translation system.