This study aimed at determining whether airway responsiveness (AR) tests performed by use of barometric whole body plethysmography (BWBP) were repeatable in cats and to what extent AR was affected by the nebulization protocol used, the age of the animals, the inflammatory status of the airways and prior bronchodilator treatment. Repeatability of AR was tested on two occasions in 30 healthy cats. The concentration of carbachol inducing a 300% increase of the enhanced pause (Penh)--an estimator of airflow limitation--was calculated (C-Penh300) and did not differ significantly between the two tests (0.035+/-0.017% compared to 0.034+/-0.016%) and was significantly and positively correlated. The comparison between rapidly and slowly increasing carbachol concentrations was performed in ten healthy cats and showed a significantly lower C-Penh300 (%) when slowly increasing concentrations were used (0.037+/-0.013% compared to 0.039+/-0.015%, P<0.05). A significant age-related increase of C-Penh300 was evidenced by performing AR tests in 15 healthy cats at 12, 18, 24 and 30 months (12 months: 0.026+/-0.008%, 18 months: 0.031+/-0.009%, 24 months: 0.038+/-0.01%, 30 months: 0.043+/-0.014%, P<0.05). C-Penh300 significantly decreased in 12 Ascaris suum-sensitised cats after allergen exposure (0.026+/-0.016% compared to 0.033+/-0.016%, P<0.05) and was negatively correlated with the granulocyte percentage of bronchoalveolar lavage fluid (r=-0.36, P<0.01). Compared with a placebo inhalation, pre-treatment with inhaled salbutamol significantly increased C-Penh300 in four healthy cats (0.093+/-0.021% compared to 0.036+/-0.004%, P<0.05). This study provides evidence that AR determination by use of BWBP is promising as non-invasive indicator of lower airway inflammation or for monitoring response to bronchodilator treatment.