Instrumental and historical data on mainshocks for 13 seismogenic sources in western Anatolia have been used to apply a regional time- and magnitude-predictable model. Considering the interevent time between successive mainshocks, the following two predictive relations were computed: log T (t) = 0.13 M (min) + 0.21 M (p) - 0.15 log M (0) + 2.93 and M (f) = 0.87 M (min) - 0.06 M (p) + 0.33 log M (0) - 6.54. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.29, respectively, for the first relation, and 0.65 and 0.47, respectively, for the second relation. The positive dependence of T (t) on M (p) and the negative dependence of M (f) on M (p) indicate the validity of time- and magnitude-predictable model on the area considered in this study. On the basis of these relations and using the occurrence time and magnitude of the last main shocks in each seismogenic source, the probabilities of occurrence P(Delta t) of the next main shocks during the next 50 years with decade interval as well as the magnitude of the expected main shocks were determined. The highest probabilities P (10) = 80 % (M (f) = 6.8 and T (t) = 13 years) and P (10) = 32 % (M (f) = 7.6 and T (t) = 29 years) were estimated for the seismogenic source 11 (Golhisar-Dalaman-Rhodes) for the occurrence of a strong and a large earthquake during the future decade, respectively.