The paroxysmal explosive event which occurred at the SE Crater on 5 January 1990 was one of the most important explosive events which has occurred on Mt. Etna in the last two centuries. This event was the first of three. Subsequent investigations furnished data used to draw up a map of the distribution of the material emitted and indicate that: a) the main explosive column axis with ejection of lava blocks, bombs, scoria, lapilli and ash was inclined to the WNW; b) ash was scattered by a strong SSE wind beyond the Tyrrhenian Coast (50-60 km) and scoria were found as far as 20 km away from the volcano; c) total volume of the pyroclastics ejected was estimated to be about 15X10 <sup>6</sup> m <sup>3</sup> . Study of the volcanic tremor revealed that the phenomenon had a shallow origin beneath the Summit Craters. This exceptional eruptive event was compared with others recorded in the last two centuries in order to try to interpret the eruptive mechanism.