Thirty years since its inception, the Earned Income Tax Credit (EITC) has become a robust and largely successful component of American labor and antipoverty policy. This research brief reviews the structure and history of the EITC, summarizing key research into the people and places it affects as well as its impact on important socioeconomic measures. The brief concludes by examining several issues surrounding the credit, and outlines proposals intended to improve the effectiveness of the EITC as it enters its fourth decade.