CONTEXT Reported cases of legionellosis more than tripled between 2001 and 2012 in the United States. The disease results primarily from exposure to aerosolized water contaminated with Legionella. OBJECTIVE To identify and describe policies and guidelines for the primary prevention of legionellosis in the US. DESIGN An Internet search for Legionella prevention guidelines in the United States at the federal and state levels was conducted from March to June 2012. Local government agency guidelines and guidelines from professional organizations that were identified in the initial search were also included. SETTING Federal, state, and local governing bodies and professional organizations. RESULTS Guidelines and regulations for the primary prevention of legionellosis (ie, Legionnaires' disease and Pontiac fever) have been developed by various public health and other government agencies at the federal, state, and local levels as well as by professional organizations. These guidelines are similar in recommending maintenance of building water systems; federal and other guidelines differ in the population/institutions targeted, the extent of technical detail, and support of monitoring water systems for levels of Legionella contamination. CONCLUSIONS Legionellosis deserves a higher public health priority for research and policy development. Guidance across public health agencies for the primary prevention of legionellosis requires strengthening as this disease escalates in importance as a cause of severe morbidity and mortality. We recommend a formal and comprehensive review of national public health guidelines for prevention of legionellosis.