It was more than twenty years ago that the hypothesis was formulated l'haI' there was a collective use of an «entheogen » or «hallucinogem> in the ancient rites of the Eleusinia17 Mysteries; a cult that developed and lasted in Greece for a couple ofmillennia. In this study the author intend to criticaliy look again, correct and bring up to date the data, the discussions and the hypothesis proposed up to now on the drugs of the Eleusinian culto At the height of the complexity of the Eleusinian Mysteries we find ourselves facing a «psychopharmacological complex» involving at least two and up to six different psychoactive agents. The ergot hypothesis of Wasson and colieagues contains some imprecision and will be re-presented here in a revised version as one of the most plausible hypothesis today concerning the oldest and most secret psychoactive agent of the Eleusinian Mysteries.