RATIONALE AND OBJECTIVES: Quantitative regional measurement of physiological parameters of lung may improve both early detection of asthma and its response to treatment by elucidating the characteristics of airway obstruction. Recent emergence of hyperpolarized helium-3 magnetic resonance imaging as a sensitive pulmonary imaging tool has shown great potential in capturing important structural and functional aspects of normal and diseased lungs. The objective of this study was to investigate regional ventilation changes in the mouse lung following allergen sensitization and challenge. MATERIALS AND METHODS: A murine model of allergic airway inflammation was created in mice following allergen challenge using Af and IgE-mediated asthma. The creation of model was verified using pulmonary function test and histology. Regional fractional ventilation was then measured in the animals using hyperpolarized 3He MRI on a pixel-by-pixel basis with a planar resolution of 0.24 mm. The sensitized and healthy animals were then compared statistically to assess the potential sensitivity of this technique in detection of such pulmonary abnormalities. RESULTS: In this work, we have demonstrated for the first time the quantitative measurement of regional ventilation in normal and asthmatic mice. Results of this study show significant changes in regional ventilation in murine model of allergic airway sensitization compared with that in normal control animals. CONCLUSION: Further development of this technique can potentially serve as a quantitative marker to investigate the physiology of allergen-induced airway hyperresponsiveness and to assist in disease treatment and prevention.