With premiums increasing for private health insurance, questions have been raised about the extent to which increases are justified. Oversight of the private health insurance industry is primarily the responsibility of states. In 2010, the Patient Protection and Affordable Care Act required the Department of Health and Human Services (HHS) to award grants to assist states in their oversight of premium rates. GAO was asked to provide information on state oversight of premium rates. In this report, GAO describes (1) states' practices for overseeing health insurance premium rates in 2010, including the outcomes of premium rate reviews; and (2) changes that states that received HHS rate review grants have begun making to enhance their oversight of premium rates. GAO surveyed officials from insurance departments in 50 states and the District of Columbia (referred to as states) about their practices for overseeing premium rates in 2010 and changes they have begun making to enhance their oversight. GAO received responses from all but one state. GAO also interviewed officials from California, Illinois, Maine, Michigan, and Texas to gather additional information on state practices. GAO selected these states based on differences in their authority to oversee premium rates, and proposed changes to their oversight, their size, and their geographic location. GAO also interviewed officials from advocacy groups and two large carriers to obtain contextual information.