Two adults and two children with life-threatening asthma refractory to maximal standard therapy were treated with the inhalational anesthetic agent isoflurane. In each case, the temporal response to the initiation of therapy was striking. All patients survived and none experienced adverse reactions attributable to the drug. Rapid therapeutic benefit, minimal side effects, absence of cumulative toxicity, and ease of administration are factors supporting the use of isoflurane for patients with severe asthma.