Kraepelin already challenged his dichotomy of psychoses, because in clinical practice too many cases were not in line with his pattern. Different terms for these disorders were coined. Leonhard separated cycloid psychoses from other forms of endogenous psychoses. The idealized subtypes (anxiety-beatific, hyperkinetic-akinetic-motility and confusional exited-inhibited) are characterized by a bipolar course with complete recovery. Operationalised criteria were developed by Perris. We report on a 60 year old woman diagnosed as schizophrenic in 1984/1985 and 2006. In August 2015 she was admitted with stupor and mutism and therefore was treated with fluphenazine and lorazepame. Six days later the clinical picture changed, she became confused and very agitated. After change of treatment to benperidole her clinical condition improved within 12 days. After 3 further days she became confused, agitated and euphoric again. The symptoms persisted in spite of a change of treatment to haloperidole. After diagnostic revision therapy was augmented with lithiumcarbonate. Six days later the psychotic symptoms began to improve and were completely remitted after 10 further days. The case report points out that a differential-diagnostic revision of an apparently therapy-resistant schizophrenia should not only be carried out according to ICD 10 criteria but a cycloid psychosis should be taken into account, too. Perris-criteria are contrasted with ICD 10-criteria for schizophrenia and mania with psychotic symptoms. Symptomatology and clinical course in our patient fulfilled exactly the Perris-criteria. We recommend an augmentation trial with lithium in acute phases of cycloid psychoses by all means before ECT.