The mortality due to asthma is gradually increasing in Denmark. In 1988, 209 patients died from asthma. Of these patients, 108 were under 70 years. Information about patients who died from asthma in Danish intensive care units (ICU) in 1988 was obtained retrospectively by questionnaires. 99% of all the ICU's replied. Eleven of the abovementioned patients died in an ICU because of inadequate oxygenation or ventilation. In cases where an anaesthesiologist was called to a patient with acute severe asthma, who subsequently died from the disease, the majority had developed cardiac arrest, when the anaesthesiologist arrived. The use of objective monitoring of the degree of pulmonary obstruction by use of peak flow measurements and series of arterial blood gas values is recommended. Hypoxemia, the main risk factor, might be revealed in time by measurements of pulseoximetry. If the arterial PCO2 is increasing, the patient should be monitored in an ICU in view of oxygenation and ventilation, and possibly mechanical ventilation.