Marked increases in the awareness, treatment, and control of high low-density lipoprotein (LDL) cholesterol occurred among United States (US) adults from 1988-1994 to 1999-2004. An update to the Third Adult Treatment Panel guidelines was published in 2004, and it is unknown if these improvements have continued since the publication of these revised treatment recommendations. The aim of this study was to determine trends in the awareness, treatment, and control of high LDL cholesterol among US adults from 1999-2000 to 2009-2010 using nationally representative samples of US adults aged ≥20 years from 6 consecutive National Health and Nutrition Examination Surveys (NHANES) in 1999-2000 (n = 1,659), 2001-2002 (n = 1,897), 2003-2004 (n = 1,698), 2005-2006 (n = 1,692), 2007-2008 (n = 2,044), and 2009-2010 (n = 2,318). LDL cholesterol was measured after an overnight fast, and high LDL cholesterol and controlled LDL cholesterol were defined using the 2004 updated Third Adult Treatment Panel guidelines. Awareness and treatment of high cholesterol were defined using self-report. Among US adults, the prevalence of high LDL cholesterol did not change from 1999-2000 (37.2%) to 2009-2010 (37.8%). Awareness of high LDL cholesterol increased from 48.9% in 1999-2000 to 62.8% in 2003-2004 but did not increase further through 2009-2010 (61.5%). Among those aware of having high LDL cholesterol, treatment increased from 41.3% in 1999-2000 to 72.6% in 2007-2008 and was 70.0% in 2009-2010. Among US adults receiving treatment for high LDL cholesterol, the percentage with controlled LDL cholesterol increased from 45.0% in 1999-2000 to 65.3% in 2005-2006 and had decreased slightly by 2009-2010 (63.6%). In conclusion, high LDL cholesterol remains common among US adults. Additional efforts are needed to prevent high LDL cholesterol and increase the awareness, treatment, and control of high LDL cholesterol among US adults.