Antigen presenting cells (APCs) such as dendritic cells (DCs) and macrophages comprise a relatively small fraction of leukocytes residing in lymphoid and non-lymphoid tissues. Accordingly, functional analyses of these cells have been hampered by low cell yields. Also, alveolar macrophages share several physical properties with DCs, and this has complicated efforts to prepare pure populations of lung APCs. To overcome these difficulties, we have developed improved flow cytometry-based methods to analyze and purify APCs from the lung and its draining lymph nodes (LNs). In this chapter, we describe these methods in detail, as well as methods for culturing APCs and characterizing their interactions with T cells.