The multiple organ dysfunction syndrome (MODS) is mainly caused by sepsis--community acquired or more frequently by nosocomial infections acquired on the intensive care unit. Further causes are intoxications, burns and multiple trauma. MODS worsens the prognosis of intensive care patients. We report on four cases of MODS developing outside hospital as a result of sustained tachycardia. Severity of MODS was apparently dependent on the duration of tachycardia and was rapidly reversible after termination of the tachycardia. Our observations show that sustained tachycardia may also cause MODS.