This study uses an innovative methodology and six waves of "Schools and Staffing Survey" data spanning two decades (1988-2008) to assess the potential of midcareer entrants--teachers who enter the profession from careers outside of education--to diversify teaching, staff public schools, and fill vacancies in high-need subjects. We find that the percentage of midcareer entrants among first-year teachers nearly doubled between 1988 and 2008 and that midcareer entrants comprise more than one third of incoming public school teachers. Despite this influx, midcareer entrants have not substantially diversified the teaching workforce. These findings have implications for teacher preparation, induction, and policies aimed at diversifying teaching.