Data on the relationship between nasal and bronchial reactivities are scarce. This study aimed at investigating a possible influence of the nasal provocation test on bronchial reactivity. Three groups of eleven subjects each were examined: patients suffering from allergic rhinitis with no clinical evidence of asthma, workers exposed to respiratory irritants complaining of occupational rhinitis and asthma, and healthy subjects. Non-specific bronchoprovocation was performed before and after nasal challenge with histamine. The bronchial challenge with histamine solutions (0.125 mg/ml and 128 mg/ml) was performed by the five-breath cumulative method (Chai H. et al. J Allergy Clin Immunol 1975;56:323-7). Non-specific nasal provocation was performed by spraying doubling concentrations of histamine (0.125 mg/ml-32 mg/ml) into both nostrils at three-minute intervals. The reaction was monitored by measurement of nasal inspiratory peak flow, nasal resistance, and nasal spirometry. The level of non-specific nasal reactivity was significantly lower in patients with allergic rhinitis than in the other two groups. The bronchial reactivity of the "rhinitis" group and of those occupationally exposed to irritants was significantly lower than among healthy subjects. An immediate and significant decrease in bronchial reactivity could be observed after nasal challenge in the group of healthy subjects as well as in workers exposed to irritants, but there was no significant change in bronchial reactivity among patients suffering from allergic rhinitis.