Legionella pneumophila is a relatively common cause of both community-acquired and healthcare-associated pneumonia. Clinical manifestations are nonspecific, but high fever, diarrhea, and hyponatremia are often distinctive. Diagnostic modalities include culture on selective media and urinary antigen detection. Quinolone and macrolide antibiotics are highly effective when initiated early in the course. Endemic healthcare-associated Legionnaires’ disease is often underdiagnosed and overlooked. Infection has been linked to drinking water distribution systems of acute care and extended care facilities, with warm water systems typically implicated. Health departments, public agencies, and industry organizations have issued guidelines aimed at preventing outbreaks of Legionnaires’ disease. These guidelines include diagnostic testing for Legionella infection, building risk assessments and water management plans and programs, and culturing of the drinking water distribution system. Superheating and flushing or hyperchlorination of the water distribution are short-term approaches to terminate an outbreak. Long-term systemic water treatment with copper-silver ionization, chlorine dioxide, and monochloramine has also been shown to be effective in controlling Legionella. Proactive culturing of the water distribution system for Legionella when cases of healthcare-associated Legionnaires’ disease have not been discovered is an evidence-based approach to prevention.