The MCAT is a standardized test that assesses a prospective medical student's knowledge, and is used by medical schools to evaluate applicants. The USMLE, however, is the national licensing examination. Current medical students are allowed to take the exam, but passing the exam grants licensure only after students have completed their medical programs. Furthermore, because these exams represent opposite ends of the educational process, there is an issue of expiration. For example, most medical schools will not accept MCAT scores that are more than three years old. Because you take the USMLE either during or after medical school, however, once you pass all three steps, your score doesn't expire.
The MCAT is made up of 144 multiple-choice questions, not including 32 optional trial questions -- questions being tested for use on future exams, and 12 satisfaction survey exams. The total test time is approximately 5 hours and 10 minutes, including all breaks, tutorials and agreement sections.
The USMLE, however, is a complex, three-part examination. Step one includes multiple-choice questions that test your basic scientific knowledge. Step two is broken into two sections: the Clinical Knowledge portion is a computer-based, multiple-choice test, while the Clinical Skills portion is a practical exam of 15-minute patient encounters administered at one of five regional test centers. Step three is a two-day test: On the first day you'll have eight hours to complete 366 multiple-choice questions, and then eight hours on the second day to complete 144 questions as well as 12 computer-based case simulation questions.
The MCAT is divided into three specific subject areas, and are presented on the exam in the following order: Physical Sciences, Verbal Reasoning and Biological Sciences. The content on the USMLE, however, is remarkably complex. Step one focuses on basic science and organ systems. The Clinical Knowledge portion of step two focuses on normal growth and development and individual disorders. The Clinical Skills portion of step two tests your ability to gather information from patients and asses their conditions. Step three integrates content from steps one and two to test your ability to perform as an unsupervised physician.
These exams also hold different criteria for determining eligibility. To take the first two steps of the USMLE, you must either be currently enrolled in, or a graduate of, a U.S. or Canadian medical school leading to a Doctor of Medicine or Doctor of Osteopathic Medicine degree accredited by either the Liaison Committee on Medical Education or the American Osteopathic Association, or meets eligibility requirements of the Educational Commission for Foreign Medical Graduates. To take step three of the USMLE you must pass steps one and two and obtain your doctorate degree. The MCAT, however, asks only that you intend to apply to a health professions school. In fact, you can even apply for special permission to take the exam, which can be for any reason other than applying to health professions school.