We analysed earthquakes at Mt. Etna for the period 1983–1991 using a method that weights uncertainties in hypocentral location. Three-dimensional distributions of ‘hypocentral probability’ and ‘energy density’ were studied, and two first-order volcano-tectonic structures identified. The first, on the northern and western sides, is roughly NE–SW oriented, and strongly marks the northernmost limit of earthquake occurrences in the volcano region; the second, NNW–SSE trending, affects the south-eastern flank of the volcano, and is evidence for an almost aseismic uprise of magma along it. Both structures fit well with the geodynamic framework of eastern Sicily. On the contrary, there is no evidence for a main magma chamber, as postulated in the literature.