This study has analysed the occurrence of hyperreractivity and airway remodelling in a model of asthmatic disease in brown Norway rats sensitized to Dermatophagoides pteronyssinus allergen (D pter). Male brown Norway rats (250-300 g) (n=7) were sensitized by 2 subcutaneous injections of D pter (50 IR/ml) (Stallergenes AS, France) and Al2O3 at days 0 (D0) and 3 (D3), followed at D17 by intratracheal instillation of D pter. Control (C) rats (n=5) underwent the same protocol but with saline solution instead of D pter. Witness (W) rats (n=5) were not submitted to any treatment. At D24, enhanced expiratory pause (Penh), used as an index of airway resistance, was measured using a barometric plethysmograph for conscious animals. At D25, rats were killed, a bronchoalveolar lavage (BAL) was performed, and isometric contraction was measured on rings isolated from trachea (T), extrapulmonary (EPB) and intrapulmonary bronchi (IPB) using an organ bath system. Maximal contraction (Fmax) and LogEC50 were derived from cumulative concentration response curves to -8 to-3 LogM carbachol (CCh). Wall thickness and smooth muscle area of proximal and distal bronchi were measured on Masson’s trichrome stained serial paraffin slides of lung. Results are expressed as mean ± SEM. Statistical comparisons were done by non parametric tests using SPSS software. Differences were considered significant when P < 0.05. Allergen challenge increased Penh in S, but not in C and W rats. In vitro stimulation by D pter induced contraction of T, EPB and IPB rings isolated from S, but not C and W rats. In response to metacholine (MCh) challenge, MCh concentration (in LogM) inducing 300 % increase in Penh was significantly lower in S (-4.36 ± 0.44) and C (-3.92 ± 0.54) versus W (-2.86 ± 0.55) rats. Fmax to CCh was significantly higher in IPB from S (1966 ± 232 mg/mg wet weight) versus C (1613 ±189 mg/mg ww) and W rats (1191 ± 113 mg/mg ww), and LogEC50 (in LogM) significantly lower (S: -6.22 ± 0.03; C: -5.64 ± 0.02; W: -5.23 ± 0.02). In BAL fluid, cellular density was significantly higher in S (334 ± 52 cells/µl) versus C (217 ± 18 cells/µl) and versus W (165 ± 52 cells/µl) rats, as was the percentage of eosinophils (S: 8.75 %; C: 1.74 %; W: 0.7 %) and mast cells (S: 0.5 %; C: 0.2 %; W: 0 %). No significant difference was found for bronchial wall thickness and smooth muscle area between S and W rats. Sensitized rats showed (i) in vivo and ex vivo specific bronchoconstriction to allergen stimulation, (ii) in vivo hyperresponsiveness and ex vivo hyperreactivity and hypersensitivity to cholinergic stimulation, and (iii) increased proportion of eosinophils and mast cells in BAL fluid, indicating that such sensitized rats are a relevant model of asthma. Absence of significant morphometric change indicates that airway hyperresponsiveness associated change occurs prior to airway remodelling.