USMLE vs. COMLEX: What’s the Difference?

Last updated on June 7th, 2023

USMLE vs. COMLEX: Is one exam for MD students and the other for DO students? It’s not that simple.

Traditionally speaking, osteopathic medical students have been required to take the COMLEX (Comprehensive Osteopathic Medical Licensing Examination) to be eligible for licensure, whereas allopathic medical students are required to take the USMLE (United States Medical Licensing Exam) in order to obtain their medical license.

However, the situation is more complex. As a medical student, taking board examinations serves a dual purpose for one’s career trajectory: to obtain a medical license and also to be a competitive applicant for residency programs. Most competitive subspecialties have historically attracted more allopathic students and as such, have evaluated prospective candidates based exclusively on USMLE scores. However, recent changes have altered the test-taking landscape.

In 2018, the American Medical Association (AMA) approved a resolution establishing USMLE and COMLEX exam equivalency ^[1]. The stated goal of this resolution was to increase acceptance of the COMLEX exam among all residency programs. Another recent development towards this goal occurred in 2020, when the American Osteopathic Association (AOA) and American Association of Colleges of Osteopathic Medicine (AACOM) were integrated into a single accreditation system for residency programs: under the umbrella of the Accreditation Council for Graduate Medical Education (ACGME).^[2,^3]

What Do These Recent Developments Mean?

Currently in 2023, with the exception of some neurosurgery programs, all osteopathic students who have passed the COMLEX are now eligible to apply to all US residency training programs. All allopathic students applying to residency programs will be in the same candidate pool with their osteopathic colleagues.

Ultimately, the final decision about which candidates are selected to any given residency program lies with each Program Director. Despite this stated equivalence, the reality remains that many competitive specialties, for example, in neurosurgery, dermatology, interventional cardiology, and others, still largely favor the USMLE over the COMLEX.

If you are a DO medical student interested in applying to a competitive specialty, it likely will be in your professional interest to take both the USMLE and COMLEX. Similarly, certain fellowship programs still use USMLE scores to evaluate candidates.

What Do the Exams Have in Common?

Both exams rigorously test the fundamentals of medicine.
Both are computer-based exams administered internationally at Prometric Testing Centers.
The cost of both exams is comparable: $660 for the USMLE (Step 1) and, starting in May 2023, $715 for the COMLEX (Level 1).

Comparison of USMLE and COMLEX Scores

As of May 2022, both USMLE Step 1 and COMLEX Level 1 exams have shifted to a pass/fail scoring system. The thresholds for passing each exam are as follows:

COMLEX Passing Score: 400
USMLE Passing Score: 194 (in general, this translates to approximately 60% of questions correct)

Neither exam will release scores immediately upon completion on exam day. Test takers will be notified by email when scores become available:

COMLEX Score Release: 3-4 weeks post-exam
USMLE Score Release: 4-6 weeks post-exam

How Do COMLEX and USMLE Exams Differ in Exam Content?

While both exams test clinically-relevant principles of basic science, the COMLEX integrates Osteopathic Manipulative Medicine (OMM) into many of the questions. Furthermore, the COMLEX more heavily focuses on the musculoskeletal (MSK) system as well as pathology commonly encountered in a primary care setting. If taking both exams, you should have a firm grasp of the content you will encounter on each exam which can be reviewed on these websites:

In addition to course content, you should also familiarize yourself with the different manner in which concepts will be tested. An efficient way to do so is by taking practice exams offered by the National Board of Osteopathic Medical Examiners (NBOME) and the National Board of Medical Examiners (NBME) for the COMLEX and USMLE, respectively:

Generally speaking, COMLEX questions are written in a more direct, fact-based format. Candidates get a sense of “either you know it, or you don’t” after reading the question stem. The USMLE, on the other hand, structures questions using a stepwise approach. Each question typically requires use of significant logic and reasoning, with extreme attention to detail. One or two seemingly superfluous details can be critical for discerning the correct answer from a similar, albeit wrong answer choice.

How Do USMLE and COMLEX Differ in Exam Structure?

There are several important differences in the way each exam is structured on exam day:

Total Testing Time: The COMLEX (Level 1) is administered over the course of 9 hours including breaks while the USMLE (Step 1) is administered over 8 hours including breaks.
Number of Questions: The COMLEX features 400 total questions (divided into 8 blocks), whereas the USMLE has only 280 questions (divided into 7 blocks).
Time per Question: The COMLEX allows less time (60 minutes per 50-question block), thus providing 72 seconds per question, whereas the USMLE allows for more time per question (60 minutes per each 40-question block), thus providing 90 seconds per question on average.
Block Timer: The COMLEX is divided into a 4-block morning session and a 4-block afternoon session. The test taker is allowed 4 hours per session, which they can budget however they like. For example, it is possible to spend 75 minutes on the first block of the morning session. However, that extra 15 minutes will cut into the time remaining for the other three blocks in the session. This is in contrast with the USMLE, where each block will end abruptly after 60 minutes.
Break Timer: While the COMLEX allows flexibility with budgeting time spent on question blocks within a given session, the USMLE allows more flexibility with budgeting break time. If the tutorial is skipped (recommended), the USMLE allows for 60 minutes total break time on exam day. This break time may be taken in any amount between any blocks, according to the preferences of the test taker. Alternatively, the COMLEX break times are predetermined: 10 minutes following the first two blocks of the morning session, 40 minutes for lunch, and 10 minutes following the first two blocks of the afternoon session.

Key Takeaways:

The decision to take USMLE, COMLEX, or both should be tailored to your individual career goals.
There are key differences in exam content and structure.
The exam day experience is much different for the COMLEX vs USMLE.