Since the early 1970s, Giancarlo Arnao, as a doctor and expert, counter-informed the most widespread illegal drug already in our society: cannabis, known in Western culture with the names of hashish and marijuana.He did this first by proposing, like no other then and few even today, the state of international scientific research (because Italian ones have never existed).The themes: toxicity, the so-called question of passing drugs, the reduction of harm.This manual, several times updated until the disappearance of Arnao, taught several generations of young people how to understand the substance not to abuse it and not to be afraid of it.To them, as to parents and teachers.