Disorders of involuntary movement due to psychotropic drugs pose a major problem when treating mentally ill patients. These adverse drug reactions (ADR) frequently undermine the patients' compliance and may have serious consequences as well. The drug safety program in psychiatry AMSP (Arzneimittelsicherheit in der Psychiatrie) surveyed a population of 122,562 patients between 1993 and 2000, and documented 129 especially severe or uncommon involuntary movement disorders (IMD): 9 episodes of severe acute dyskinesia, 32 of severe Parkinsonism, 5 of especially severe akathisia, 16 of 'atypical dyskinesia', 38 of Pisa syndrome, 6 of catatonic neuroleptic syndrome, 15 of neuroleptic malignant syndrome, and 8 of tardive dyskinesia. The epidemiological data for this population were systematically analyzed as regards the patient's history of medication, comedication, and clinical course. In those cases, in which a certain drug was imputed to cause an ADR alone and the causal relationship was rated as definite or probable, typical neuroleptics with mainly antipsychotic effects showed a relatively high incidence of 0.1047 %, those with hypnotic-sedative effect a lower incidence of 0.0198 %, and the atypical neuroleptics an incidence of 0.0567 %. This difference was highly significant in an chi (2)-analysis (chi (2) = 18.81, df = 2, p < 0.0001). Our data provide important information on the frequency, severity, and the consequences of ARD for the patients' compliance, and thus are of clinical interest.