A group of 153 patients with bronchial asthma were subjected to bronchial provocation and intracutaneous tests with allergen from the gram negative bacterium Erwinia herbicola which commonly occurs in organic dusts. Of this group, 80 persons were also examined with both tests with the allergen of Aspergillus fumigatus and 96 persons with the house dust extract. The frequency of positive skin reactions to the tested allergens was much greater than that of the positive bronchial reactions. No significant correlation was found to exist between the frequency and intensity of the bronchial and skin reactions except for delayed and late reactions to Erwinia herbicola. The authors conclude that bronchial provocation tests represent a much more specific and reliable method in the assessment of the clinical status of patients with extrinsic asthma than do skin tests.