The dibenzoepine derivative clozapine is seen as a prototype of an atypical neuroleptic, because clozapine has good antipsychotic efficacy but only minimal dopamine antagonistic properties in common animal paradigms. The latter is reflected by the observation that extrapyramidal symptoms during clozapine are a rare phenomenon. Furthermore, recent studies in the USA demonstrated a superior efficacy of clozapine in schizophrenic patients who are nonresponsive to classic neuroleptics. Therefore, the introduction of clozapine in the USA was performed in 1990 despite the well-known risk of agranulocytosis (1-2% during the first year of treatment); however, under restricted conditions regarding the mandatory weekly control of the white blood cell count. For the use of clozapine in Europe, it should be underlined that in 1992 the indication was restricted to "acute and chronic forms of schizophrenia" whereas formerly it was permitted to treat several other neuroleptic resistant syndromes with clozapine, e.g. severe psychotic excitement, aggressive behavior or manic or atypical psychosis. The usage of clozapine in these indications is now only permitted under the restricted legal conditions of a "therapeutic trial" in selected patients. However, several indications for which clozapine has been used successfully in Europe are currently re-investigated in the USA, hopefully leading to a redefinition and extension of the indication spectrum. On the other hand, the American multicenter trials lead to the conclusion that the treatment with clozapine is not furthermore the treatment of last choice but a serious therapeutic alternative which should be available for all schizophrenic patient in case of neuroleptic resistance or of severe side effects of standard neuroleptics. Clozapine treatment leads to an improvement of the quality of life in one third of these schizophrenics and, moreover, results in a marked reduction of costs mainly by reducing the rehospitalisation rates. On the other hand, the list of well-known side effects of clozapine (e.g. agranulocytosis, increased risk of seizures, initial sedation) has to be extended (e.g. transient leucocytosis or eosinophilia, rare but severe complications like cardiorespiratory arrest and "sudden death" during combination with benzodiazepines, case reports of pericarditis, pancreatitis or polyserositis). On the background of possible cardiorespiratory complications we recommend to start the first treatment with clozapine in high risk patients (e.g. those in older age or in case of organic brain impairment) only in restricted indications and only in centers with sufficient clozapine experience.