Františkovy Lázně is world-renowned as a spa. The salutary effects of the springs were known from the 15th century on. First, the water was used locally for salutary purposes, later sold all over Germany. In 1700, it reportedly sold more water than all other German spas combined. In the year 1793, the town was officially founded under the name Kaiser Franzensdorf (Emperor Francis II's village) and later renamed to Franzensbad, under which name it became a famous spa.
Until their expulsion in 1945 the majority of the population of the city was German (see Sudetenland).
The local natural mineral water has a relatively high content of dissolved carbon dioxide. The effects of the carbonic baths are shown in the better performance of the cardiovascular system, in the mild decrease of blood pressure in the pulse, in the lower occurrence of chronic inflammatory processes in the body, and also in terms of rheumatics, and in the improved blood circulation in tissues and the vegetative stabilisation.
The local mud treatments represent a traditional curative method which has thermal, chemical and mechanical effects. The mud treatment consists of a thick mushy combination of mud and mineral water which is heated up to a temperature which is significantly higher than body temperature. The treatment has a positive effect on mobility of muscles and the pain in treated tissues.
The local Spa corporation is the biggest spa corporation in the Czech Republic.