The rupture zone of the MW 6.5 earthquake of 26 July 2001 in the North Aegean Sea (NAS) is oriented northwest-southeast and occupies the southwestern part of the seismic zone of NAS. The motion indicates reverse faulting with a significant sinistral strike-slip component. A review of the past NAS seismicity reveals that in the last 150 yr the seismicity is strongly clustered in time with 14 out of 15 pre-2001 events being members of a cluster. Only the 1912 earthquake is an isolated event. This implies that the probability of the 2001 earthquake being the first member of a new time cluster is 0.93, which is the probability for the next NAS strong earthquake to occur within a time interval equal to the mean interarrival time of cluster events: 2.9 ± 2.06 yr. The distribution of the earthquake rupture zones and the position of the 2001 event suggest that the next event may rupture one of the unruptured parts of NAS to the northeast of the 2001 earthquake.