LSD was introduced in psychiatry in the 1950s. Between 1960 and 1973, nearly 400 patients were treated with LSD in Denmark. By 1964, one homicide, two suicides and four suicide attempts had been reported. In 1986 the Danish LSD Damages Law was passed after complaints by only one patient. According to the Law, all 154 applicants received financial compensation for LSD-inflicted harm. The Danish State Archives has preserved the case material of 151 of the 154 applicants. Most of the patients suffered from severe side effects of the LSD treatment many years afterwards. In particular, two-thirds of the patients had flashbacks. With the recent interest in LSD therapy, we should consider the neurotoxic potential of LSD.