The aim of the study was to establish the level of the nonspecific nasal responsiveness in a group of workers (N = 84) occupationally exposed to respiratory irritants, and to compare it with its level in healthy subjects (N = 60). Another goal was to study the effect of occupational exposure to irritants, smoking, and atopy on nonspecific nasal responsiveness. The modified method of nonspecific nasal provocation with histamine developed by van Wijk and Dieges (Clin Allerg 17:563-570, 1987) was used. The method was performed by spraying doubling concentrations of histamine (0.03-32 mg/mL), starting with saline, in a cumulative manner into each nostril. The reaction was measured by total nasal resistance ("opening" interruption technique). The result of the test was expressed as provocation concentration of histamine that caused > or = 75% rise of total nasal resistance compared to its value measured after saline. We found a significantly higher percentage of nasal hyperreactors and a significantly greater nonspecific nasal responsiveness among 65 exposed workers (chi 2 = 78.6; p < 0.001, t = -5.48; p < 0.001, respectively) than in the group of healthy subjects. A significantly (t = 4.25; p < 0.001) increased nonspecific nasal responsiveness was observed during exposure when compared to nonspecific nasal responsiveness assessed after 2 weeks out of exposure, when tested in 19 patients. Higher smoking rate as measured by smoking category (number of cigarettes multiplied with years of smoking) was associated with the lower levels of nonspecific nasal responsiveness. Also, we failed to confirm a relation between atopy and nonspecific nasal responsiveness in a group of workers exposed to irritants.