During a 7-week microearthquake experiment conducted in Epirus, Akarnania, and the Ionian islands of western Greece, we located approximately 600 earthquakes with magnitudes between 2 and 4.2. No event was deeper than 40 km. The seismicity cannot be clearly associated with any single fault except the Lixourion right-lateral fault located west of the Ionian islands. Focal mechanisms of about 100 earthquakes show, for a narrow band of earthquakes located along the coast, ENE-WSW shortening consistent with the surface tectonics. Farther east, focal mechanisms shown NNW-SSE extension beneath the foothills of the Pindus mountains, which is unrelated to surface faulting but is consistent with the presently subsiding basins. This strain pattern is seen far north and south of the Lixourion fault and is similar to the one observed in the Peloponnese. It suggests that a large-scale mechanism is responsible for the recent geodynamics of both the northwestern and southwestern Aegean. ¿ American Geophysical Union 1995