Dapsone (4,4'-diaminodiphenylsulfone) is an aniline derivative belonging to the group of synthetic sulfones. In 1937 against the background of sulfonamide era the microbial activity of dapsone has been discovered. Shortly thereafter, the use of dapsone to treat non-pathogen-caused diseases revealed alternate antiinflammatory mechanisms that initially were elucidated by inflammatory animal models. Thus, dapsone clearly has dual functions of both: antimicrobial/antiprotozoal effects and anti-inflammatory features similarly to non-steroidal anti-inflammatory drugs. The latter capabilities primarily were used in treating chronic inflammatory disorders. Dapsone has been investigated predominantly by in vitro methods aiming to get more insights into the effect of dapsone to inflammatory effector cells, cytokines, and/or mediators, such as cellular toxic oxygen metabolism, myoloperoxidase-/halogenid system, adhesion molecules, chemotaxis, membrane-associated phospholipids, prostaglandins, leukotrienes, interleukin-8, tumor necrosis factor α, lymphocyte functions, and tumor growth. Moreover, attention has been paid to mechanisms by which dapsone mediates effects in more complex settings like impact of lifespan, stroke, glioblastoma, or as anticonvulsive agent. Additionally, there are some dermatological investigations in human being using dapsone and its metabolites (e.g., leukotriene B4-induced chemotaxis, ultraviolet-induced erythema). It could be established that dapsone metabolites by their own have anti-inflammatory properties. Pharmacology and mechanisms of action are determining factors for clinical use of dapsone chiefly in neutrophilic and/or eosinophilic dermatoses and in chronic disorders outside the field of dermatology. The steroid-sparing effect of dapsone is useful for numerous clinical entities. Future avenues of investigations will provide more information on this fascinating and essential agent.