Two patients were presented at our hospital with hypothermia following dose adjustment of antipsychotic medication. The first patient, a mentally retarded 45-year-old man developed a temperature of 31.7 degrees C several days after starting of levomepromazine. The second patient, an 41-year-old schizophrenic man, whose risperidone dose had been increased following a psychotic crisis, developed deep hypothermia (temperature 29.7 degrees C) and severe respiratory insufficiency requiring pressure support ventilation. Both patients were admitted to the ICU and recovered completely. Antipsychotics influence hypothalamic thermoregulation and may induce hypothermia by stimulating dopamine (mainly D2) receptors and blocking 5-HT2 receptors. Furthermore, antipsychotics may reduce the shivering capability and can cause peripheral vasodilatation and reduced shunting by blocking skin alpha 1 receptors. Hypothermia can be a lethal condition. When a patient's clinical condition deteriorates following the start of antipsychotic medication, the presence of hypothermia should be excluded.