Historical and instrumental data of the last five centuries show that major earthquakes in the Marmara Sea area are followed by high strong-earthquake seismicity in the Aegean area. During the first phase of this excitation period, which lasts about 3 years, strong shallow earthquakes concentrate almost exclusively along the Northern Boundary of the Aegean plate. Within 1--5 years after the first strong earthquake along this boundary, strong-earthquake seismicity also increases in the Eastern Aegean Boundary. On the basis of current ideas on active tectonics and the previous observations, we expect the generation of several mainshocks with a mean magnitude of M=6.5 along the Northern Aegean Boundary during the next 3 years, following the recent large Izmit (NW Turkey) earthquake (1999.8.17, M=7.4). ¿ 2000 American Geophysical Union