Among the core transitions in medical education is the one from medical school to residency. Despite this challenging transition, the final year of medical school is known as lacking structure and clarity. The authors examine the preparation of medical students for the professional and personal challenges of internship in the context of transition courses. They first describe the development of a residency transition course, offered since 2001 at the University of California, San Francisco, School of Medicine (UCSF), exploring aspects of a needs assessment, course goals and content, core competencies, and course implementation. They then critically analyze the course, judging it successful based on high subjective satisfaction scores and increased perceived preparedness data. Next, the authors discuss the national context of transition courses, perspectives of various stakeholders, and lessons learned from the UCSF experience. Finally, they consider future directions, suggesting that internship transition courses be a standard part of the medical school curriculum.