This paper investigates Japanese trade to see whether the J/S-curve phenomenon between net exports and the terms of trade is observed in the data from 1980Q1 to 2008Q3. Based on the results of a VAR stability test, the aggregate trade data are endogenously split into three sub-period data sets, with the J/S-curve present in the last two. The J/S-curve may stem from the increasing share of China and the oil-exporting countries in Japanese trade. In fact, the J/S-curve is observed in the bilateral trade data with those countries but not in the data with Korea or the United States.