With the aid of a computerized anaesthetic record-keeping system, the incidence of laryngospasm during anaesthesia was studied, in order to quantify the risk of this complication. 136,929 patients given 156,064 anaesthetics were studied. There were 1,232 cases of laryngospasm recorded in 1,197 patients. The incidence of laryngospasm was calculated in subgroups characterized by age, sex, preanaesthetic conditions, premedication, anaesthetic technique, type of surgery and concomitant complication. An incidence exceeding 50 laryngospasms in 1,000 patients was observed when giving anaesthesia to children with bronchial asthma, with airway infection, in those who had a previous anaesthetic complication, during oesophagoscopy and when correction of hypospadias was performed. Extirpation of skin tumours and scars in males 50-59 years old was also accompanied by a similarly high incidence. Figures exceeding 25 laryngospasms in 1,000 patients were seen in the age group 1-3 months and in children undergoing appendicectomy, oral endoscopy and plastic surgery, when tracheal intubation had been performed and when a gastrointestinal tube was used. In the age group 50-59 years, an incidence exceeding 25 in 1,000 patients was seen when there had been preoperative airway obstruction and in females when the anaesthetic technique included spontaneous breathing and face mask, or apneic oxygenation. Dilatation of the anal sphincter and mediastinoscopy in males were also associated with an increased incidence of laryngospasm.