This paper describes 19 consecutive episodes (18 patients) of status asthmaticus managed in a medical intensive care. Eleven patients required mechanical ventilatory support [MV] and 2 (11%) died. Most patients had acute respiratory acidosis although arterial blood gases alone could not predict the need for MV. The peak inspiratory airway pressure measured during MV was a useful index of the severity of underlying lung disease. The most serious complication of MV was barotrauma. On follow up studies, two distinctive patterns of chronic asthma could be identified. One group of patients had highly labile pulmonary function with unpredictable and wide changes in peak flow rates while another group had poorly reversible obstruction.