This paper describes efforts to introduce teachers to three aspects of problem-based learning: (1) learning cases; (2) student-centered learning; and (3) small group cooperative learning. Problem-based learning was woven into the design of professional development institutes because of the organizers' idea that as teachers grow professionally in a problem-based learning environment, they develop a deeper conceptual understanding of problem-based learning and increase their confidence in using this type of approach. Field observations collected on the teacher participants' implementation of problem-based learning showed evidence that elementary teachers especially increased instructional time spent on science lessons. Contains 19 references. (WRM)