Behaviorism was the dominant epistemology in education approximately 20 years ago, while constructivism has most recently been the dominant epistemology in the field. In this paper, differences between the assumptions of behaviorism and constructivism are briefly identified, and the behaviorist pedagogy of Individually-Guided Education and the constructivist pedagogy of Problem-Based Learning are analyzed across six core elements of the instructional environment, including learning goals, instructional approaches, teacher's role, students' roles, resource utilization, and evaluation strategies. In conclusion, the authors discuss the similarities in pedagogy resulting from two very different epistemologies. (Contains 32 references.) (Author/MES)