"R&D Alert" covers issues affecting schools in the Western Regional Educational Laboratory's four-state region--Arizona, California, Nevada, and Utah--and throughout the United States. This issue of "R&D Alert" shares what WestEd is learning from a sample of their latest work, focusing on three points in the process: preservice, inservice, and teacher retention. This issue's lead article, Knowledge Know How Needed for Teacher Quality, shares lessons about improving teacher quality through ongoing professional development. It describes how two WestEd projects help teachers develop "pedagogical content knowledge," a blend of subject-specific knowledge and skills that research has shown to be key particularly for teachers helping students learn mathematics and science. This is issue also includes, "Rethinking Teacher Preparation," an excerpt from a recent WestEd Policy Perspectives report on bringing new teachers into the profession. A third article in this issue, Working Conditions Key for Teacher Retention, focuses on what schools and districts can do to retain more of these teachers. In particular, the article describes the importance of work conditions (including an effective professional development system, administrative support, and a climate of collegiality) for keeping high-quality teachers on the job.