MS4 stands for “fourth-year medical student,” the final year of the standard four-year Doctor of Medicine (MD) program in the United States. While the first two years (MS1 and MS2) focus on classroom science and the third year (MS3) introduces students to hospital rotations, the fourth year is largely about choosing a specialty, applying to residency programs, and preparing for the transition from student to physician.
How MS4 Differs From Earlier Years
The biggest shift in the fourth year is flexibility. MS3 students rotate through required clerkships in surgery, internal medicine, pediatrics, psychiatry, and obstetrics/gynecology on a fixed schedule. MS4 students, by contrast, build much of their own schedule from elective rotations, sub-internships, and research time. That freedom serves a practical purpose: students need open weeks for residency interviews, licensing exams, and audition rotations at programs they hope to match into.
Clinical autonomy also changes, though not as dramatically as many students hope. Third-year students learn the management styles of different specialties largely by observing and presenting patients. Fourth-year students on sub-internships take on more responsibility, sometimes writing admission orders and coordinating with care teams. In practice, though, their notes are often unread and unsigned, and they cannot independently start or stop treatment plans. The real leap in responsibility comes later, on the first day of residency.
Sub-Internships and Audition Rotations
A sub-internship (or “sub-I”) is the closest an MS4 gets to functioning as an intern. Students typically complete at least one in their chosen specialty, managing a small panel of patients with graduated independence. Residency program directors consistently recommend a sub-internship in the student’s intended career field, along with rotations in internal medicine, critical care, and emergency medicine, regardless of specialty choice.
Many students also pursue “away rotations” at hospitals where they hope to train for residency. The AAMC runs a system called Visiting Student Learning Opportunities (VSLO) that lets students search for and apply to short-term clinical rotations at other institutions across the country. These audition rotations give students a chance to impress a program’s faculty in person, and they give programs a longer look at potential applicants than a single interview day allows. Away rotations are especially common in competitive surgical specialties where personal connections carry significant weight.
The Residency Application Process
Residency applications dominate much of the MS4 calendar. The process runs through the Electronic Residency Application Service (ERAS), which opens in early June. Students can begin submitting applications to programs in early September, and programs start reviewing those applications later that month. From October through January, students travel for interviews, sometimes attending 10 to 20 across the country depending on specialty competitiveness.
After interviews wrap up, students submit a ranked list of their preferred programs to the National Resident Matching Program (NRMP). Programs submit their own ranked lists of preferred applicants. A computer algorithm then pairs students and programs, and results are revealed on Match Day, typically in mid-March. Students who don’t match in the initial cycle enter the Supplemental Offer and Acceptance Program (SOAP), a rapid process during Match week where unfilled programs interview and extend offers to unmatched applicants over just a few days.
Licensing Exams and Graduation Requirements
Most MS4 students take Step 2 CK of the United States Medical Licensing Examination during the summer before or early in the fourth year. Step 2 CK tests clinical knowledge and the ability to apply medical concepts to patient care scenarios. While Step 1 (taken after the preclinical years) shifted to pass/fail scoring in 2022, Step 2 CK remains numerically scored and has taken on greater importance in residency applications as a result. Many medical schools require a passing Step 2 CK score before granting the MD degree.
Transition to Residency Training
A growing number of medical schools now require a capstone course in the final weeks before graduation, designed to bridge the gap between student and intern. These courses, sometimes called “Transition to Residency” or “boot camps,” typically run about four weeks and combine morning lectures on practical medical management with afternoon hands-on workshops and simulations.
The procedural training is notably concrete: students practice placing IVs and central lines, performing ultrasound-guided procedures, suturing, inserting chest tubes, and drawing arterial blood gases. Simulations cover airway emergencies, acute care scenarios, and mock pages from nurses, replicating the kinds of decisions interns face on overnight call. Many programs also include specialty-specific sessions, such as laparoscopic skills for future surgeons or casting and splinting for those entering orthopedics. Beyond clinical skills, these courses address wellness and burnout, handoff communication, patient safety reporting, and navigating electronic health records.
The Financial Picture at Graduation
By the time MS4 students walk across the stage, most carry substantial educational debt. For the class of 2024, the median debt among indebted graduates was $205,000 overall, with public school graduates carrying a median of $200,000 and private school graduates at $230,000. Private school debt rose 5% from the prior year. These figures only capture students who borrowed; about 25% of medical graduates finish without education debt, typically due to family support, scholarships, or military service obligations.
What MS4 Students Actually Spend Their Time On
Focus group research with fourth-year students reveals that the year serves several overlapping purposes beyond clinical training. Students use it for career identification, exploring subspecialties they may not have encountered during required third-year clerkships. They seek out diverse practice settings, from rural clinics to urban trauma centers, to refine what kind of medicine they want to practice long term. Many also describe anxiety about competence as a real motivator in course selection, choosing rotations specifically to fill gaps they worry about before starting residency.
The schedule itself is uneven. Early fall is packed with away rotations and application preparation. Late fall and winter revolve around interviews, which can mean weeks of travel with little clinical work. After Match Day in March, the final months often carry a lighter clinical load, sometimes earning the nickname “senior vacation,” though the transition-to-residency courses increasingly fill that space with structured training. By late May or early June, MS4 students become physicians, and most begin residency on July 1.