COMLEX vs. USMLE: What’s the Difference?
Learn about the differences between the COMLEX and the USMLE and decide which to take for your career goals.
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Part 1: Introduction to the difference between the COMLEX and the USMLE
For medical students in the United States, the path to licensure involves rigorous exams that test both knowledge and clinical skills. Two of the most common exams are the COMLEX (Comprehensive Osteopathic Medical Licensing Examination) and the USMLE (United States Medical Licensing Examination).
While both exams serve as gateways to medical licensure, they are designed for different types of medical students and have distinct structures, content, and purposes. Understanding the differences between these exams is crucial for students deciding which path to take. This is especially true for those in osteopathic (DO) programs who may need to choose between taking only the COMLEX or both the COMLEX and the USMLE. In this guide, we’ll discuss the key differences between the COMLEX and the USMLE exams to help you make a decision as to which is best for your situation.
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Part 2: COMLEX vs. USMLE
COMLEX and USMLE are both multi-step exams designed to assess medical knowledge and clinical skills, but they cater to different types of medical students.
COMLEX is specifically designed for DO students and incorporates osteopathic principles and practices (OPP), including manipulative treatment techniques. The USMLE, on the other hand, is the standard licensing exam for MD students and focuses on general medical knowledge and clinical application.
Both exams are required for licensure in their respective fields. DO students must pass all levels of the COMLEX to practice medicine, while MD students must pass all steps of the USMLE. It is important to note that sometimes DO students choose to take the USMLE in addition to the COMLEX, especially if they are applying to competitive residency programs or programs that prefer USMLE scores.
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Part 3: Key differences between COMLEX and USMLE
Structural differences
The structure of the COMLEX and USMLE differs in terms of format, timing, and question style. COMLEX Level 1 is a nine-hour exam that includes multiple-choice questions and Clinical Decision-Making cases, which require written responses. COMLEX Level 2-CE is a one-day computer-based exam lasting approximately nine hours. COMLEX Level 3 is a two-day exam totaling roughly 14 hours.
In contrast, the USMLE Step 1 is an eight-hour exam taken in one day and consisting entirely of multiple-choice questions. USMLE Step 2 CK is a one-day exam lasting approximately nine hours. USMLE Step 3 is a two-day exam lasting approximately nine hours.
As you can see, both exams are lengthy, but since the COMLEX allows less time per question, that alone can make pacing more challenging for some students.
Another key difference lies in the style of the questions. USMLE questions are known for being clear, concise, and logically structured, often presenting a patient case followed by straightforward answer choices. COMLEX questions, on the other hand, are often longer, more abstract, and include osteopathic-specific content, such as manipulative treatment techniques. Additionally, as a side note, the COMLEX embeds normal lab value ranges directly into the question stem, whereas the USMLE requires students to reference a separate table for this information.
Content differences
While there is significant overlap in the content covered by the COMLEX and USMLE, there are also notable differences. Both exams test foundational medical knowledge, clinical sciences, and patient care, but the COMLEX places a strong emphasis on osteopathic principles and manipulative treatment. For example, students taking the COMLEX must be familiar with diagnosing and treating conditions using osteopathic manipulative medicine, a skill that is not tested on the USMLE.
The USMLE, however, tends to distribute its questions more evenly across various organ systems and clinical scenarios. This even distribution allows for a broader assessment of general medical knowledge.
Additionally, the USMLE’s case-based questions often simulate real-world clinical decision-making, making it a preferred exam for residency programs that value practical application of knowledge. (For DO students preparing for both exams, it’s important to focus on the unique content areas of each test to ensure comprehensive preparation).
Preparation differences
The perceived difficulty of both the COMLEX and USMLE varies depending on the student’s background and preparation. The COMLEX is often considered more challenging due to its abstract question style and the inclusion of osteopathic-specific content, which can feel unfamiliar. Additionally, COMLEX questions sometimes include “wildcard” scenarios that are difficult to anticipate, making preparation more unpredictable.
While the USMLE is more structured, it is known for its rigorous, case-based questions that require critical thinking and application of knowledge. Many students find the USMLE’s clear format easier to navigate, but the depth of knowledge required can make it equally challenging. For DO students taking both exams, preparation can be particularly demanding, as they must master both general medical knowledge and osteopathic principles.
To prepare effectively, you should use resources tailored to each exam. For the COMLEX, tools like COMBANK by TrueLearn are invaluable for mastering OMM and osteopathic-specific content. For the USMLE, resources like UWorld and AMBOSS are widely regarded as essential for success. By leveraging the right study materials and creating a structured study plan, you can maximize your performance on both exams.
Final thoughts
Both the COMLEX and the USMLE are critical exams for medical students, but they serve different purposes and cater to different audiences. The COMLEX is designed specifically for osteopathic students and emphasizes osteopathic principles, while the USMLE is the standard for allopathic students and focuses on general medical knowledge. Ultimately, the choice between the COMLEX and USMLE—or whether to take both—should be guided by your long-term aspirations. By understanding the differences between these exams and preparing strategically, you can set yourself up for success on your journey to becoming a licensed physician.
About the Author
Dr. Shirag Shemmassian is the Founder of Shemmassian Academic Consulting and one of the world's foremost experts on medical residency admissions. For over 20 years, he and his team have helped thousands of students match to top residency programs using his exclusive approach.
