The current study used survey instruments to examine the changes in PBL PD participants’ self-efficacy and teaching practices. The results indicated that teachers’ selfefficacy in teaching science improved over the course of the PBL PD. It was also found that the PD influenced how the teachers taught in their schools. The teacher participants reported that at the end of the PD, they used more standards-based teaching practices, informal assessments, projects, communication, calculators/computers, and the Internet than they did prior to participating in the PD. The study also looked at whether teacher characteristics played a role in the changes in their self-efficacy and teaching practices.