Allergic asthma is characterized by airway hyperresponsiveness and lung inflammation. To better understand disease pathophysiology, lung inflammation is monitored in animal models, and in this regard, non-invasive medical imaging is emerging for use in pre-clinical research. The primary aim of this project is to develop protocols using non-invasive fluorescent optical imaging to quantitate lung inflammation in response to allergic challenge in a murine model of asthma. Our studies show that in vivo optical imaging provides a meaningful, non-invasive measure of lung inflammation, including dye specific enzymatic activity such as for cathepsins, in murine models of allergic asthma. This approach is a new option for repeated measurements in individual animals for drug testing and development.