A 42-year-old woman with bronchial asthma since childhood was admitted to hospital because of severe dyspnoea. Emergency bronchoscopic intubation had to be performed for life-threatening inspiratory and expiratory stridor. This demonstrated that the larynx was covered by a dirty-grey membrane and the vocal-cord gap was narrowed to a mere slit. As laryngeal diphtheria was suspected 2000 IU/kg diphtheria antitoxin was administered together with 1 mega U penicillin G four times daily intravenously. On the same day, Corynebacterium ulcerans, a very rare cause of diphtheria, was isolated from a coughed-up piece of the membrane. Toxic, massive swelling of the lymph nodes and soft tissues of the neck necessitated maintenance of an open upper airway by intubation and (later) tracheostomy for 41 days. A week later the patient was discharged without any permanent defect.