Asthma is a chronic inflammatory disease. We propose to study inflammatory changes in the lungs of subjects with atopic asthma of different severity in vivo using positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG). It has been shown that the uptake of FDG as detected by PET scanning correlates with inflammation in animal models as well as in human disease processes such as sarcoidosis, tuberculosis and abscess formation. In addition, it has been shown that the inflammation associated with allergen challenge in patients with atopic asthma can be visualized using PET scanning with FDG. We hypothesize that the degree of FDG-uptake as a measure of inflammation correlates with the severity of asthma as determined by pulmonary function tests and clinical signs and symptoms. In addition, information about the spatial distribution of the inflammatory changes will be obtained. To compare the characteristics of the inflammation in asthma with non-asthmatic inflammation of the lung, the images obtained in asthmatic subjects will be compared with images from subjects who have inflammatory changes of the lung caused by Wegener's granulomatosis. Subjects with atopic asthma and non-atopic control subjects will be selected from the community and, if eligible for the study, undergo skin testing against common allergens and pulmonary function testing. Subjects with Wegener's granulomatosis will be selected from a large group of subjects followed with this disease at NIAID. PET scanning with FDG will be used to measure inflammation in the PET scanning facility at the Clinical Center of the NIH and the results of the scanning will be correlated with the severity of the disease. We expect that for the first time this methodology will permit an objective measure of the basic pathogenic process, the allergic inflammation, in patients with atopic asthma. Using this methodology it will be possible to study the efficacy of currently available therapies for allergic inflammation. In addition, this methodology will provide an extremely useful tool for the development of new therapeutic approaches to the treatment of asthma.