A patient with acute lymphatic leukaemia developed a bilateral fulminating Pseudomonas aeruginosa pneumonia and required controlled ventilation of the lungs. Marked agitation, hypotension and bronchospasm unresponsive to conventional bronchodilators presented a therapeutic challenge. A continuous intravenous infusion of midazolam failed to provide adequate sedation. A continuous intravenous infusion of ketamine resulted in better sedation, an increase in arterial pressure and a diminution of bronchospasm. The clinical improvement was maintained for the 5 days during which ketamine was infused. Plasma concentrations of ketamine and its metabolites are reported.