Neuroleptic malignant syndrome (NMS) is the most dangerous side effect of phenothiazines therapy. In the period of time from 1995 to 2002 in the Intensive Toxicological Unit there were five patients, 3 men and 2 women, aged from 25 to 62 (average 44.2) years-old, admitted from the regional inpatients psychiatric units with the diagnosis of pneumonia and/or sepsis. The patients about 48-72 hours before admittance were given some phenotiazine derivatives (promazine, perphenazine, clozapine, pipamperon) and/or buthyrophenone (haloperidol) because of psychotic state. Altered consciousness, muscle rigidity, hyperpyrexia (39.0-41.0 degrees C), sweating, tachycardia (120-150/min.), tachypnoea (respiratory rate more than 25/min.) and high level of creatine kinase activity (23,751-112,288 U/l) dominated. Only one patient had clinical picture of pneumonia. Because of the rapid development of acute respiratory failure, respirathorotherapy was initiated and continued for 8 and 10 days in two patients respectively. Transient thrombocytopenia (26,000/microliter) in one subject was observed. The neuroleptic drug was withdrawn and intensive supportive care with administration of bromocriptine (15-20 mg/24 h) was provided. None one of the doctors told the patients about the possibility of NMS during phenothiazines therapy.