Background/Context: Recent research has shown the importance of professional development for teacher learning and has documented the qualities that make professional development effective for improved instruction and student achievement. But there is little research to suggest how the policy environment shapes teachers' choices to participate in either "effective" or "ineffective" professional development. Because No Child Left Behind (NCLB) and related reforms are making new demands on teachers, and professional development is one of the critical mechanisms by which we intend to improve our educational system, it is important that we find the most effective ways to encourage teachers to participate in the types of professional development most likely to improve their practice--and, in turn, student achievement. Purpose: In describing the policy environment on several dimensions, we seek to discover which types of policies are more or less influential in moving teachers into the types of professional development that research has shown to be most effective for improved teaching and learning. In addition, we examine whether these relationships differ for a high-stakes subject, mathematics, and a low-stakes subject, science. We characterize the policy environment based on a theory that suggests that certain attributes of the policy environment increase policy implementation: (1) authority--the extent to which a policy is persuasive; (2) power (or accountability)--rewards and sanctions attached to a policy; (3) consistency--how aligned a policy is with other elements in the policy system; and (4) stability--how stable actors and ideas in the policy environment are. Our analyses answer two main questions. Do attributes of the policy environment--authority, power, consistency, and stability--influence the likelihood that teachers will participate in professional development with research-based features of effectiveness, rather than classroom management or no professional development? Is this relationship between policy attributes and professional development participation different for high-stakes subjects (e.g., mathematics) than for lower stakes subjects (e.g., science)? Research Design: Using a national sample of high school mathematics and science teachers from the Schools and Staffing Survey (SASS), we conduct a secondary analysis using a three-level hierarchical linear model (HLM) to predict teachers' level of participation in different types of professional development activities. Conclusions: We find that authority, not power, is associated with teachers taking the kind of professional development that we know improves teaching and learning--activities focused on subject matter content and instructional strategies, as well as active interactions with other teachers around curriculum and instruction. Similarly, we find that stability (measured by reduced teacher turnover), not the consistency of professional development with other reforms, is associated with taking effective professional development. We offer our findings to contribute to understanding how best to shape policy to provide the most useful opportunities for teacher learning.