Recruitment and retention challenges are once again leading to teacher shortages across the nation. Especially in urban and rural school districts, low salaries and poor working conditions often contribute to the difficulties of recruiting and keeping teachers, as can the challenges of the work itself. As a consequence, in many schools--especially those serving the most vulnerable populations--students often face a revolving door of teachers over the course of their school careers. Many of these teachers are underprepared for the work of teaching and learning. In districts that meet shortages by hiring teachers who have not completed an adequate preparation, turnover is higher, as novices without training leave after their first year at more than twice the rate of those who have had student teaching and rigorous preparation. Similarly, teachers who are left to sink or swim on their own leave teaching at much higher rates than those who receive supportive mentoring in their first years on the job. Under these circumstances, everyone loses: student achievement is undermined by high rates of teacher turnover and by teachers who are inadequately prepared for the challenges they face. Schools suffer from continual churn, undermining long-term improvement efforts. Districts pay the costs of both students' underachievement and teachers' high attrition. Newly emerging teacher residency programs seek to address these problems by offering an innovative approach to recruiting and retaining high-quality teachers for hard-to-staff schools. This report summarizes the features of these programs and research about their practices and outcomes. [For the policy brief to this report "Teacher Residencies: Building a High-Quality, Sustainable Workforce. Policy Brief," see ED606355.]