No evidence has emerged which suggests that the principles of immunity derived from studies on cells from other body sites are contradicted in the lung and its associated lymphoid tissue. What is clear, however, is that the environment dictates the types of cells, their relationship to one another, and what perturbing events will set in motion either the development of an "active" immune response or tolerance. Investigating mechanisms for the development of lung immunity has increased our understanding of how human diseases develop and is continuing to suggest new ways to manipulate pulmonary immune responses. Demonstration that lung cells regulate both nonspecific inflammation and immunity through the expression of adhesion molecules and the secretion of cytokines offers hope for ways to design more effective vaccines, enhance microbial clearance in immunosuppressed hosts, and to suppress manifestations of immunologically mediated lung disease. Important lung diseases targeted for intensive research efforts in the immediate future are tuberculosis, asthma, and fibrotic lung disease. Perhaps even the common cold might be conquered. Considering the pace of current research on lung immunity, it may not be too ambitious to predict that these diseases may be conquered in the next decade.