Abstract  In two patients with chronic schizophrenia, who were on clozapine medication for more than 6 months, a sudden withdrawal of the drug resulted in a very pronounced deterioration of the psychosis within 24–48 h. The most prominent symptoms were auditory hallucinations and persecutory ideas and one patient tried to commit suicide. These observations are interpreted as supersensitivity psychoses induced by the very effective clozapine treatment.