Bronchial asthma represents an increased airways responsiveness to various stimulants, leading to reversible obstruction of expiratory flow and chronic inflammatory changes in airways wall. Ketamine has been demonstrated to lower airway resistance and to increase lung compliance in the asthmatic patients. In several studies and case reports it has been used successfully in the management of status asthmaticus, resistant to conventional therapy, but so far no clinical trial has been carried out to support this empirical use of ketamine. For this reason, we designed a prospective observational study.Eleven, 15-40 years old patients, with status asthmaticus whose respiratory failure did not respond to conventional therapy and mechanical ventilation (after 24h), were entered in this study (provided that there were not any contraindications to ketamine use). These patients received ketamine at a loading dose of 1 mg/kg (IV), followed by a continuous infusion of 1 mg/kg/hr for 2h. Peak airway pressure, PaCO2 and PaO2 were measured prior to ketamine administration, 15min after administration and 2h after infusion of ketamine. Mean peak airway pressure and PaCO2 significantly decreased 15min and 2h after administration and infusion of ketamine (p<0.005) and PaO2 significantly increased in these time intervals (p<0.005).Ketamine is a useful and safe drug in the intensive treatment of status asthmaticus. However, ketamine should only be used for asthmatics whose respiratory failure does not respond to standard therapy.