The objective of the study was to compare triggers for asthma attacks in a group of intrinsic (IA) and extrinsic asthmatic (EA) subjects. We included 205 asthmatic patients divided, according to skin-prick tests, in a group (n = 63) of IA and a group (n = 142) of EA. The questionnaire provided information on associated conditions (nasal polyps and intolerance to aspirin) as well as on allergenic and nonallergenic triggers. Data analysis demonstrated that in IA, some airborne nonallergenic factors were significantly more often involved. In addition, this association did hold true when comparing subgroups of patients with normal baseline FEV1 values. For those subjects, PC20 and the slopes of the dose-response curves to metacholine were comparable. In conclusion, the higher sensitivity of a group IA subjects to some nonallergenic factors is not related to a lower baseline spirometric value in this subgroup. It may be hypothesized that, in these patients, sensitivity of airways irritant receptors might be increased.