Legionnaires' disease (LD) can be nosocomial, community acquired or travel related. The source of Legionella infection is potable water systems that become colonized by the microorganism. Prevention studies involved mainly hospital water systems. Different strategies have been suggested but none are fully successful: engineering modifications, heating of water to temperatures above 59 degrees C, heating and flushing the plumbing with hot water (80 degrees C), water chlorination, silver-copper ionization of the water, UV-light disinfection of water, instant heating in order to avoid hot-water tanks and others. LD is widely underdiagnosed because laboratory methods are specific and suspicion index is usually low; therefore, the appropriate tests are not requested. In addition, all methods present limitations. No randomized controlled trials have been performed to study the treatment of legionellosis but comparative observational studies have been published, mostly involving community-acquired cases. Macrolides and quinolones presented similar results when comparing important outcomes, such as mortality and complications.