In 1922, a neurodegenerative disease was named after the German doctor Julius Hallervorden, who, with his colleague Hugo Spatz, had first described it. In 1996, a campaign requested that his name be erased because of the work of Hallervorden in the Nazi regime. He had not directly participated to the so-called “Euthanasia operation” that killed mentally ill people but had received 2000 brains for the victims in order to sustain his research. This article describes how this knowledge about Hallervorden was slowly built. In 1945, Hallervorden did not deny having received the brains but refused to take any responsibility of the killings. Untill his death in 1965, he systematically opposed the dissemination of any information about his past. He was supported in this by all his German colleagues.