In atopic patients with chronic non specific lung diseases, the sensitivity of the bronchial tree to histamine and to allergens was studied by means of inhalation provocation tests. An unmistests takable correlation was demonstrated between the results of histamine inhalation provocation tests tests (HIPT) and allergen inhalation provocation tests (AIPT).When the HIPT revealed a higher sensitivity to histamine, the AIPT disclosed a higher sensitivity to allergens. This was manifested by the larger number of allergens to which the patients reacted at AIPT, as well as by the severity of the reaction after AIPT, as measured spirographically. Moreover, higher sensitivity to histamine was associated with more late positive reactions after AIPT