Foreshock activity preceding strong (M > 5) main
shocks in the Corinthos Gulf, Central Greece, is examined
from primarily a data set of 1970-1998 and supplementary
fromdatasetsof 1785-1910and 1911-1969.Ithasbeenfound
that foreshock activity appears at time T < 4 months before
the main shock. The last 10 days of the foreshock period is the most
important phase since the probability for the main shock occurrence
at any time within that time window is very high
exceeding 0.83. The duration of the foreshock period as well
as the largest foreshock magnitude are both independent of
the main shock magnitude. Obtained results are important for
inclusion in probabilistic earthquake predictions in the
Corinthos Gulf.