Volumes 5 and 6 of the Handbook of Labor Economics will systematically review the research topics, empirical findings, and methods that constitute frontier research in the field. The focus will be on the most important research advances that have taken place since the publication of the previous Handbook Volume 4 almost 15 years ago. - How do factors such as trade, technology, skills, immigration, crime, unions, race, and gender affect wages and employment in modern labor markets? - What is the labor market impact of policy interventions such as minimum wages, employment and training policies, and family policies? - Recent methodological advances in empirical methods and models of the labor market in the presence of imperfect competition