Background: Health care-associated infections (HAIs) affect 5% of patients hospitalized in the United States each year. Central line-associated bloodstream infections (CLABSIs) are important and deadly HAIs, with reported mortality of 12% to 25%. This article provides national estimates of the number of CLABSIs among patients in ICUs, inpatient wards, and outpatient hemodialysis facilities in 2008 and 2009 and compares ICU estimates with 2001 data. Methods: To estimate the total number of CLABSIs among patients aged 1 year or older in the United States, Centers for Disease Control and Prevention (CDC) multiplied central line use and CLABSI rates by estimates of the total number of patient-days in each of 3 settings: ICUs, inpatient wards, and outpatient hemodialysis facilities. CDC identified total inpatient-days from the Healthcare Cost and Utilization Project's National Inpatient Sample and from the Hospital Cost Report Information System. Central line use and CLABSI rates were obtained from the National No ocomial Infections Surveillance System for 2001 estimates (ICUs only) and from the National Healthcare Safety Network for 2009 estimates (ICUs and inpatient wards). CDC estimated the total number of outpatient hemodialysis patient-days in 2008 by using the single-day number of maintenance hemodialysis patients from the US Renal Data System. Outpatient hemodialysis central line use was obtained from the Fistula First Breakthrough Initiative, and hemodialysis CLABSI rates were estimated from the National Healthcare Safety Network. Annual pathogen-specific CLABSI rates were calculated for 2001 to 2009. Results: In 2001, an estimated 43,000 CLABSIs occurred among patients hospitalized in ICUs in the United States. In 2009, the estimated number of ICU CLABSIs had decreased to 18,000. Reductions in CLABSIs caused by Staphylococcus aureus were more marked than reductions in infections caused by Gram-negative rods, Candida spp, and Enterococcus spp. In 2009, an estimated 23,000 CLABSIs occurred among patients in inpatient wards, and in 2008, an estimated 37,000 CLABSIs occurred among patients receiving outpatient hemodialysis. Conclusion: In 2009 alone, an estimated 25,000 fewer CLABSIs occurred in US ICUs than in 2001, a 58% reduction. This represents up to 6,000 lives saved and $414 million in potential excess health care costs in 2009 and approximately $1.8 billion in cumulative excess health care costs since 2001. A substantial number of CLABSIs continue to occur, especially in outpatient hemodialysis centers and inpatient wards. Implications for Public Health Practice: Major reductions have occurred in the burden of CLABSIs in ICUs. State and federal efforts coordinated and supported by CDC, the Agency for Healthcare Research and Quality, and the Centers for Medicare & Medicaid Services and implemented by numerous health care providers likely have helped drive these reductions. The substantial number of infections occurring in non-ICU settings, especially in outpatient hemodialysis centers, and the smaller decreases in non-S aureus CLABSIs reveal important areas for expanded prevention efforts. Continued success in CLABSI prevention will require increased adherence to current CLABSI prevention recommendations, development and implementation of additional prevention strategies, and the ongoing collection and analysis of data, including specific microbiologic information. To prevent CLABSIs in hemodialysis patients, efforts to reduce central line use for hemodialysis and improve the maintenance of central lines should be expanded. The model of federal, state, facility, and health care provider collaboration that has proven so successful in CLABSI prevention should be applied to other HAIs and other health care-associated conditions.