We studied non-specific bronchial responsiveness (NSBR) and blood eosinophils before and 24 hours after a bronchoprovocation test (SBPT) with wheat flour (22 cases) and TDI (32 cases). Twelve patients developed asthma after exposure to wheat flour (7 early and 5 dual/late asthma), and 12 after exposure to TDI (6 early and 6 late/dual asthma). Responders and non responders to wheat flour exposure were similar for all general characteristics except IgE levels (p = 0.036) and NSBR (p = 0.047). A higher degree of airway responsiveness to methacholine was the only characteristic which differentiated responders from non responders to TDI exposure (p = 0.043). Airway responsiveness, assessed 24 hours after the SBPT (44 cases), did not show any change compared to pretest values; the data were similar both among non responders to wheat flour (Wilcoxon p = 0.1) or to TDI (p = 0.2) and responders to TDI (p = 0.6) or wheat flour (p = 0.3); also no significant changes were observed among early and dual/late asthma caused by wheat flour and TDI. Twenty-four hours after the SBPT, blood eosinophils were higher than pretest, but only among the 24 patients with asthma (Wilcoxon p = 0.002); the blood eosinophil increase was statistically significant among patients with early and late/dual asthma caused by wheat flour, and among those with early and late/dual TDI asthma. In our study, NSBR was confirmed as a common feature of occupational asthma, either IgE mediated (wheat flour) or non-IgE mediated (TDI). Twenty four hours after the specific exposure, among patients with asthma induced by wheat flour and TDI, there was an increase in blood eosinophils while in the same time interval no variation in non-specific bronchial responsiveness was observed.