An estimated 8,000-18,000 persons are hospitalized with Legionnaires disease (LD) each year in the United States, and approximately 20% of reported LD cases are associated with travel. Outbreaks of travel-associated LD can be difficult to detect because travelers disperse and Legionella-specific diagnostic tests are underutilized. Consequently, clinicians and health departments often are unaware when more than one LD case is associated with a common travel destination. In 2005, the Council of State and Territorial Epidemiologists (CSTE) adopted a position statement recommending enhanced surveillance measures for LD, with emphasis on diagnosis and reporting of confirmed travel-associated LD cases within 7 days. The rationale for enhanced surveillance was that earlier detection might lead to more rapid identification of a source (e.g., cooling tower) and expedite prevention measures (e.g., cleaning and chlorination). To 1) assess data from 32 states that used a supplementary reporting system for LD, 2) describe the epidemiology of travel-associated LD, and 3) compare characteristics of travel-associated cases with those of cases not associated with travel, CDC analyzed LD cases reported via the supplementary system during 2005-2006. The results of that analysis indicated that the proportion of LD cases that were travel associated remained stable from 2005 (23%) to 2006 (25%), the proportion of travel-associated cases reported via a dedicated CDC e-mail address increased from 11% to 24%, and the number of reported clusters of travel-associated LD increased from two in 2005 to eight in 2006. These results suggest that, to fully assess the benefits of enhanced LD surveillance, more states will need to adopt the CSTE recommendations.