Phototherapy has a very long, albeit mostly anecdotal history. Real interest in the use of ultraviolet irradiation in the treatment of various diseases started in the 19th century and reached a climax when Niels Finsen received the Nobel Prize in 1903 for his therapeutic results with lupus vulgaris. This marked the start of modern phototherapy. It was used in thermal stations for treatment of tuberculosis, in the treatment of leg ulcers in wartime, and in the treatment of skin diseases. This article reviews the history of a treatment modality that greatly changed modern dermatologic treatment, although it is as old as mankind.