The 2002--2003 Mount Etna eruption and the associated deformation provide a unique possibility to study the relationships between volcanism and volcano instability. The sequence started with movement of the eastern volcano flank and was associated with earthquakes and the formation of surface ruptures. Then the eruption occurred from fissures at the north and south rift zones and was followed by additional flank movement, seismic swarms, and surface ruptures. The overall area of flank movement implicated more than 700 km2. In this paper we investigate how episodes of magmatic events (eruptions and intrusions) and flank movement interact. In three-dimensional numerical models we simulate the volcano-tectonic events and calculate changes in the static stress field. The models suggest that the 2002--2003 events are the result of interrelated processes consisting of (1) the preeruptive intrusion of magma and inflation of the volcano, which induced (2) the movement of the volcano east flank, (3) facilitated the eruption, and (4) led to the slip of a much larger part of the eastern and southeastern flanks. Understanding the precise interconnectivity of these processes may help to forecast the behavior during future volcanic crisis at Mount Etna, which is crucial in minimizing volcanic and seismic hazards on the highly populated eastern sector of the volcano.