Nuclear factor-kappa B (NF-kappaB) is a family of DNA-binding protein factors that are required for transcription of most proinflammatory molecules, including adhesion molecules, enzymes, cytokines, and chemokines. NF-kappaB activation seems to be a key early event in a variety of cell and animal model systems developed to elucidate the pathobiology of lung diseases. The purpose of this short review is to describe what is known about the molecular biology of NF-kappaB and to review information that implicates NF-kappaB in the pathogenesis of lung disease, including ARDS, systemic inflammatory response syndrome, asthma, respiratory viral infections, occupational and environmental lung disease, and cystic fibrosis.