Legionellosis is meanwhile the most important specific water-associated infectious disease in developed countries, which is completely preventable, if water distribution systems are correctly planned and operated. This assumes clear criteria for risk regulation and for verification, including microbiological monitoring for Legionella. There are different reactive and proactive strategies in the USA and in Europe. The common premises for prevention and control of legionellosis in Germany, relevant facts for risk regulation, experience in Germany toward proactive risk regulation, and the current approach of the amended drinking water ordinance are discussed. The article concludes with a short discussion of the controversial approaches for the prevention of legionellosis in Germany.