Indium 111-labeled leukocyte scintigraphy provides an excellent noninvasive means for identifying and localizing infectious and inflammatory sites within the body. This article first compares gallium 67 citrate, the long-established radiopharmaceutical for infection imaging, to 111In-labeled leukocytes, particularly as applied to the chest. 111In-labeled leukocytes require time-consuming preparation, and the technical and practical aspects of cell labeling and imaging are reviewed in detail. The main focus of this article is the application of labeled leukocyte imaging to the evaluation of pleural, mediastinal, cardiovascular, and pulmonary disease.