This study investigates the actual usage of productive vocabulary amongst upper- intermediate Japanese learners in conversations. In order to achieve this objective, four pairs of semi-structured oonversational interviews were observed and examined by the researcher. An analysis was performed on how much intermediate and advanced Japanese vocabulary they managed to use in their conversations. The results showed that the rate of the vocabulary of JLPT level 1 and 2 was approximately 20% and the rate of the other non-JLPT vocabulary was approximately 10%.