The large percentage of Americans that rely on private health insurance for health care coverage could expand with enactment of the Patient Protection and Affordable Care Act (PPACA) of 2010. Until PPACA is fully implemented, some consumers seeking coverage can have their applications for enrollment denied, and those enrolled may face denials of coverage for specific medical services. PPACA required GAO to study the rates of such application and coverage denials. GAO reviewed the data available on denials of (1) applications for enrollment and (2) coverage for medical services. GAO reviewed newly available nationwide data collected by the Department of Health and Human Services (HHS) from 459 insurers operating in the individual market on application denials from January through March 2010. GAO also reviewed a year or more of the available data from six states on the rates of application and coverage denials and the rates and outcomes of appeals related to coverage denials. The six states included all states identified by experts and in the literature as collecting data on the rates of application or coverage denials and together represented over 20 percent of private health insurance enrollment nationally. GAO conducted a literature review to identify studies related to application and coverage denials and reviewed data from selected studies. GAO interviewed HHS and state officials and researchers about factors to consider when interpreting the data.