In problem-based learning (PBL), students working in collaborative groups learn by resolving complex, realistic problems under the guidance of faculty. There is some evidence of PBL effectiveness in medical school settings where it began, and there are numerous accounts of PBL implementation in various undergraduate contexts, replete with persuasively positive data from course evaluations. However, evidence for learning outcomes is still needed. In this chapter, the authors examine the evidence for effectiveness of the method to achieve its goals of fostering deep understandings of content and discuss the potential for developing process skills: research, negotiation and teamwork, writing, and verbal communication.