Basaltic Plinian eruptions are rare and poorly known volcanic phenomena. Etna is an active basaltic volcano, the activity of which is dominated by effusive eruptions that represent a continuous threat to a large populated area. We report on a Plinian eruption of basaltic composition that occurred in 122 b.c. Lapilli fallout caused extensive damage to the southern flank of the volcano. The discovery of this large explosive eruption raises important issues for previous hazard assessment at Etna and other basaltic volcanoes: An effusive basaltic volcano, generally nonhazardous for humans, can become very dangerous.