Clinical vampirism is named after the mythical vampire, and is a recognizable, although rare, clinical entity characterized by periodic compulsive blood-drinking, affinity with the dead and uncertain identity. It is hypothetically the expression of an inherited archaic myth, the act of taking blood being a ritual that gives temporary relief. From ancient times vampirists have given substance to belief in the existence of supernatural vampires. Four vampirists, including Haigh, the 'acid-bath murderer', are described. From childhood they cut themselves, drank their own, exogenous human or animal blood to relieve a craving, dreamed of blood-shed, associated with the dead, and had a changing identity. They were intelligent, with no family mental or social pathology. Some self-cutters are auto-vampirists; females are not likely to assault others for blood, but males are potentially dangerous. Vampirism may be a cause of unpredictable repeated assault and murder, and should be looked for in violent criminals who are self-mutilators. No specific treatment is known.