Engaging teachers in discussing and analyzing problems of practice has great potential for teacher professional development, yet little is known about how to facilitate such discussion. This study examined the strategies that experienced facilitators used to promote productive discussion among science teachers. Participants were 6 facilitators and 35 in-service teachers who participated in a professional development program that adopted a problem-based learning approach for teacher learning. Data analysis showed that experienced facilitators used a variety of strategies in their facilitation, including questioning, revoicing, making connections, clarifying, reframing, summarizing, role playing, meta-talk, and modeling. In particular, questioning and revoicing were the most important strategies in all sessions studied, accounting for about half of the facilitators' talk. Analysis further revealed both productive and disruptive characteristics of questioning and revoicing. In addition, analysis found that teachers were able to make progress in participating in the problem-based learning discourse in different ways. This study has implications for research on teacher professional development, problem-based learning, and learner-centered instruction. (Contains 7 tables.)