'Astronomers find ET civilization.' In the opinion of many, this newspaper headline could reflect what would be the most exciting, challenging and profound discovery not only of the century but of human history. The idea of a plurality of inhabited worlds in the universe is as old as our civilization. It was a religious heresy in pre-Renaissance times; Giordano Bruno was burned at the stake in 1600 because of this belief. A slow but steady increase in the number of papers on the possible existence of other beings distinct from us has been appearing since then. The rapid progress in science and technology, our although poor understanding of the mechanisms of the cosmic evolution, the consolidation of the Darwinian hypothesis and, most importantly, the tenacious work of SETI pioneers have made possibly that the scientific community took seriously the possibility of life in other places of the universe and to search for it. There are different SETI projects running in the world. The unequivocal detection of an ETI signal is the goal. This could take many forms, all of them unpredictable. Some authors notice that the unambiguous confirmation that the signal is of extraterrestrial intelligence origin would be a hard work (Boyce 1990, Tarter 1991). But of most significance is the impact on our society of such a contact. How should we react? With fear and panic because advanced ETIs would quickly destroy the human spirit? Waiting a golden age? Imagine an extraterrestrial spaceship landing somewhere in our planet. What should we do? In both cases, will human behavior be influenced by the incontestable knowledge of the existence of ETIs? As John Billingham point out 'there has been little activity on those cultural aspects of SETI other than science and engineering.'