Put simply, the USMLE Step 1 is the first of three exams — or “Steps” — that you must pass in your quest to become a licensed physician in the United States. Jointly sponsored by the National Board of Medical Examiners (NBME) and the Federation of State Medical Boards (FSMB), the test aims to assess your mastery of the basic science concepts underlying the practice of medicine. It is administered year-round at Thomson Prometric testing centers.

The Step 1 exam itself is made up of 336 questions divided into seven one-hour blocks of 48 questions each. While working within a given question block, you can skip back and forth and change your answers with impunity. Once you’ve completed a block and have proceeded to the next one, however, there’s no turning back — you can’t return to the block you just left to change or rethink your answers.

Questions on Step 1 are all multiple choice and are uniformly of the “single best answer” variety. What this means is that in many cases, more than one option available to you may be somewhat correct, but you must pick the option that does the best job of answering the question. There are no negatively phrased or matching questions on the test.