To determine the morbidity and mortality of severe asthmatic patients needing intensive care in Singapore.Retrospective review of admissions from January 1987 to March 1993.Urban teaching hospital.Forty-eight patients with forty-nine admissions with severe asthma requiring admission into the medical intensive care unit.None.Forty-eight patients with forty-nine admissions with severe asthma requiring admission into the medical intensive care unit were identified during the study period. The majority (69%) were admitted directly into the intensive care from the emergency room, and 16 cases (33%) had cardiorespiratory arrest, of whom half survived hypoxic brain damage. Mechanical ventilation was needed in 30 cases (61%), with a mean duration of 3.3 days, and 2 pneumothoraces were recorded. Those who needed mechanical ventilation had significantly higher arterial pCO2 (98 mmHg vs 62 mmHg) and a lower arterial pH (7.1 vs 7.3). However, not all patients with hypercapnia (> 50 mmHg) needed mechanical ventilation. Hospital mortality was 12% (6 cases), while two others with hypoxic brain damage died shortly after hospital discharge. Mortality was not predicted by previous need for mechanical ventilation, length of asthma, or age. For the ventilated group alone, hospital mortality was higher at 20%. On an average follow-up of 133 weeks, there was only one death. Mean potassium level was 3.9 mmol/L with 13 cases (28%) of hypokalemia (< 3.6 mmol/L).Severe asthma was associated with an appreciable mortality. Hypercapnia did not guarantee the need for mechanical ventilation. For those that survived their acute episode, there was one mortality out of 40 survivors after an average of 2 years of follow-up.