A UNIVERSAL UBIQUITOUS PHENOMENON: Because it involves many different species, inflammation is a universal phenomenon. It is also an ubiquitous phenomenon because several organs may be involved within a given species. In humans, where it is involved in almost all pathological conditions, inflammation reaches its highest degree of complexity. FOUR STEPS: Despite the diversity of symptoms and the complexity of the molecular interactions, the sequence of events leading to an inflammatory reaction involves four steps. The first is the appearance of signals initiating inflammation. The second step involves a series of cellular reactions, the earliest reactions leading to surface phenomenon. Limitation, or on the contrary amplification, of the initial inflammatory response is the third step. Finally, healing or installation of chronic inflammation is the fourth step. Transcription factors which play a switching role in cell signaling can also be useful as therapeutic targets for anti-inflammatory agents. Two transcription factors play an important role in airway inflammation: nuclear factor NF-kappa B and activating protein 1 (AP-1). Apoptosis or programmed cell death involves a cascade of events leading to condensation of the chromatin and fragmentation of the deoxyribonucleic acid. Programmed cell death is required to resolve the inflammatory process. The principal factors involved in apoptosis can be schematically divided into pro-apoptotic factors and anti-apoptotic factors.