Airway hyperresponsiveness, manifested by increased flow resistance and resulting drop in oxygen partial pressure when conducting provocation tests, is considered an early sign of a developing obstructive airway disease, an example of which is a professionally conditioned asthma. We conducted a detailed study exploring the interrelation between the respiratory mechanical parameters and the partial pressures of oxygen and carbon dioxide (PaO2, PaCO2). Reproducibility tests for the studied cardiovascular, ventilatory and respiratory mechanical parameters at rest and under various conditions of stress (external stenoses, inhalation of hypercapnic and hypoxic gas mixtures, infusion of an acetylcholine solution) showed good reproducibility of the measured data with variation coefficients < 10%. In blood gas analyses we also found comparable variation coefficients. Four groups of experimental animals were exposed for different periods of time to various working place substances (coolants, ammonium peroxodisulfate, hair bleaches [blondizing agents], isocyanates). After the exposure we checked on the bronchial sensitivity to aerosols of 0.2% and 2% acetylcholine solutions. Concomitant with an increased response of dynamic elastance, we found an increased drop in oxygen partial pressure and an almost constant carbon dioxide partial pressure, dependent on the working place substance used and on its concentration. In untreated controls the inhalation of acetylcholine resulted in bronchoconstriction and drop in oxygen partial pressure only on provocation with 2% acetylcholine. However, in the groups exposed to coolants and ammonium peroxodisulfate there was a significant drop in oxygen partial pressure already on provocation with 0.2% acetylcholine, as well as a noticeable bronchial respiratory response. The drop in oxygen partial pressure increases further after provocation with 2% acetylcholine, whereas the oxygen partial pressure dropped to a maximum of one-third of its original level by more than 10%. Placing the drop in oxygen partial pressure provoked by acetylcholine in relation to the increase in dynamic elastance, this can be well expressed by a logarithmic formula (y = -6.2. In (x) + 0.72, r = 0.96) that does not change significantly after exposure to working place substances (y = -7.0. In (x) + 3.33, r = 0.93). The close correlation of both parameters suggests that study of the oxygen partial pressures to determine the airway hyperresponsiveness should be considered important, since a marked drop in oxygen partial pressure is seen even if obstructive respiratory response is only slightly increased (slight increase in dynamic elastance). The reason for the behaviour of the blood gases is probably an increased ventilation-perfusion imbalance due to inhomogenous peripheral bronchial reactions. In the hyperresponsive animals the reactions were merely enhanced without demonstrating any differences.