One hundred and three bronchial asthma patients with a suspected allergic component developed 133 positive immediate asthmatic (bronchus-obstructive) responses (IARs) to bronchial challenge with allergen (BP). The onset of IAR was within 10 minutes, the maximum within 45 minutes, and the resolution of the response within 120 minutes after the challenge. All IARs were highly significant in comparison with the control test (p less than .01). The association of IAR with other diagnostic parameters was the following: positive disease history in 82 IAR cases (= 62%); positive immediate skin response in 91 IAR cases (= 68%); increased total serum IgE in 54 IAR cases (= 41%); positive specific IgE in the serum in 59 IAR cases (= 44%); increased serum concentration of IgG in 36 IAR cases (= 27%), of IgM in 17 (= 13%), and of IgA in 3 IAR cases (= 2%); increased blood eosinophilia in 36 (= 27%) and blood leukocytosis in 19 IAR cases (= 14%); increased bronchial reactivity to histamine in 74 of 103 patients with IAR (= 72%); body temperature increased during nine IAR cases (= 7%); and 131 IAR cases (= 98%) were accompanied by bronchial and 62 (= 47%) by general malaise complaints. The IAR showed a very good reproducibility and significant dose-response relationship (P less than .01). In conclusion, the IAR is an important diagnostic parameter for the allergic component due to immediate hypersensitivity in the bronchial tree. The correlation of other diagnostic parameters with IAR was not satisfactory. They should therefore be regarded as diagnostic supplement only.(ABSTRACT TRUNCATED AT 250 WORDS)