Unlike traditional lecture-based instruction, where information is passively transferred from instructor to student, problem-based learning (PBL) students are active participants in their own learning, thrust into unknown learning situations where the parameters of the problem may not be well-defined and the task at hand ambiguous--just like in the real world. In this article, the author discusses PBL, a student-centered approach to learning that is grounded in real-world situations. PBL involves four basic stages: (1) problem analysis; (2) self-directed learning; (3) brainstorming; and (4) solution testing. Exactly how PBL is implemented depends on the context in which learning is to take place and the preparedness of the student. In its purist form, PBL involves presenting students with an authentic problem prior to any instruction of preparation. The idea is to use the problem to introduce the concepts and problem-solving skills necessary to solve the problem.