The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized by evident morphological scarps and normal and right-lateral type movements that directly affect roads and buildings. The TF has an important role in the instability that affects the south-eastern flank of Mt. Etna, and it represents part of the southern boundary of the unstable sector. Starting from 2005, the TF has been monitored using continuous wire extensometers and by carrying out periodic direct measurements across the northern and central sectors. From 2005 to September 2009, the measurements show that the TF has undergone continuous extension of about 2-3 mm/yr. During the October 2009 to January 2010 period, the creep rate of the TF reached up to 5.5 to 7.0 mm/yr, and this was accompanied by several shallow, low magnitude earthquakes that were felt by local people. This episode appears to be linked to the increase in the sliding velocity of the eastern flank that occurred during 2009.