On October 19, 1996, a large underthrusting earthquake (Ms=6.7), the Hyuga-nada, Japan, earthquake occurred along the southern end of Nankai trough. About two months later, a second large earthquake (Ms=6.7) occurred in the adjacent region. We study the source process of the two large earthquakes in the Hyuga-nada region and compare the coseismic rupture area with aftershock distribution. The main source parameters obtained for the first mainshock are: (strike,dip,rake)=(210¿,12¿,81¿); the seismic moment Mo=2.3¿1019 Nm (Mw=6.8); the rupture area S=20¿15 km2, and the source duration T=17 s. For the second main-shock, (strike,dip,rake)=(210¿,12¿,87¿); the seismic moment Mo=1.5¿1019 Nm (Mw=6.7); the rupture area S=18¿18 km2, and the source duration T=15 s. The coseismic rupture areas do not overlap the aftershock area, while the aftershock areas of the two main-shocks mutually overlap. This implies that the common aftershock region takes a role of barriers to dynamic rupture. It is also seen that the aftershock area expanded during the first one day. ¿ 1999 American Geophysical Union