The effect of DSCG as inhibitor of the immediate allergic reaction in the bronchi was tested in provocative tests in 12 children with bronchial asthma, previously proved to have a specific hypersensitivity. The effect of the allergen provocation was assessed objectively by measurement of the airway resistance by means of a body plethysmograph. The airway resistance was measured in each child before and after inhalation of the same dose of allergen repeatedly to assess the ‘normal’ bronchial reaction for that specific allergen. Every second time the child was given DSCG before the allergen inhalation. There was always a time lapse of at least 2 days between the different trials. The results show that the usual increase in airway resistance in most cases failed to appear after the allergen inhalations that were preceded by administration of DSCG. In a few cases a less increase in airway resistance was measured, however, not of the same degree as the one usually produced by the allergen inhalations, not preceded by administration of DSCG. Thus, a marked protective effect on the asthmatic attack is evident.