Apoptosis is a form of cell death that has gained enormous attention during the past few years, and its mechanisms, important to biology and medicine, are being unraveled at an accelerating pace. Apoptosis of lung cells occurs during lung infections and may be either a host defense mechanism or reflect the pathogenesis of the infection. In the first part of this review, the biochemistry and physiology of apoptotic pathways and its regulators are discussed. This is followed by an overview of apoptotic mechanisms in selected lung infections. The implications of apoptosis in host immunity, pathogenesis, and treatment of pulmonary infections will be discussed in this context.