Case-based approaches are effective for teaching and learning science, encouraging student-directed collaborative learning and active engagement. This paper looks at using cases in science teaching and learning at the secondary and undergraduate levels and the impact these approaches have on teachers, students, curricula, and classroom organization. The particular focus is the medical school case model, also called Problem-Based Learning (PBL). The primary goal of the case group is to learn the underlying human biology within a realistic context rather than to make a medical diagnosis. The experience of 30 biology teachers working on case approaches during a 10-day course illustrates how an effort to create a new case-based strategy served as a nexus for faculty development and curriculum change in biology education. The group devised a new process of case development that blended case writing with discussion of educational goals, modes of teaching, curricular integration, and classroom organization. Several products were created, including a syllabus for a family development course on case teaching in biology; a model for curriculum development integrating case structure and student learning, classroom organization, teaching approaches and assessment; and seven second draft cases. Suggestions for additional research in cases or tools for educational change are provided. (Contains 11 references.) (ND)