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NBME CBSE: Everything You Need to Know

If you’re a medical student, you’ve probably heard of the CBSE, or Comprehensive Basic Science Examination. Some also refer to this simply as the “comp” exam. Let’s spend some time talking about what this exam is and how to prepare for it to achieve your highest score possible!

What is the NBME CBSE?

The CBSE is a standardized exam offered by the National Board of Medical Examiners that approximates the content on the USMLE Step 1 exam. It stands for “Comprehensive Basic Science Examination.”

CBSE exams are administered through your medical school and are designed to assess your knowledge from the pre-clinical years of medical training. The score you get on the CBSE is translated into a Step 1 equivalent score, which should help you get a sense of where you stand with your Step 1 preparation.

When do I take the NBME CBSE?

When you take the NBME CBSE really depends on how your medical school uses the exam. In my medical school, we took the CBSE at the end of our pre-clinical years just before our dedicated Step 1 examination time. This seems to be fairly standard at most medical schools.

For us, the CBSE score was only revealed to the examinee and was not used as any type of evaluation. Instead, the goal was solely to inform us as we designed our study schedule. Other schools require that you take and pass the CBSE before sitting for your dedicated Step 1 study period.

How long is the CBSE exam?

The NBME CBSE exam length is:

  • 184 multiple-choice questions
  • 4 blocks
  • Each block is 1 hour

Compare this to Step 1, which is:

  • 280 multiple-choice questions
  • 7 blocks
  • Each block is 1 hour

How does the CBSE compare to the real Step 1 exam?

CBSE is written by the same folks who design Step 1. However, there are some differences. The CBSE is about half the length of the real Step 1. Additionally, CBSE tends to have more “first-order” questions with short vignettes than your Step 1 prep material, but in general it is fairly similar to the real Step 1 exam.

What study materials should I use for the NBME CBSE?

Remember that the NBME CBSE is designed to mimic USMLE Step 1. So prepare for it like you would prepare for Step 1! This is a great opportunity to try out different study resources and whittle them down to those that are most useful.

Think of the CBSE as a low-stakes way to evaluate your knowledge and the success of your study strategies to date. Then, come day one of your dedicated period, you’ll be able to hit the ground running.


At this point, you have probably already looked at some Step 1 resources during your pre-clinical coursework. These may include:

  1. UWorld Step 1 question bank
  2. Sketchy
  3. First Aid for Step 1
  4. Pathoma

We recommend these resources as tried-and-true tools to help you succeed on your CBSE and Step 1. Other resources students use are OnlineMedEd, AMBOSS, Kaplan, and Boards and Beyond. Anki is a great way to review material in a spaced fashion.

For those students who need to pass the NBME CBSE prior to their dedicated study period (and are not using it as simply a formative testing experience), the best resource is the Comprehensive Basic Science Self-Assessment (CBSSA)This is the self-administered equivalent of the CBSE, which you will take during your dedicated Step 1 study period. There are currently 6 CBSSAs available: Forms 18, 20, 21, 22, 23, and 24.

Each CBSSA is:

  • 200 multiple-choice questions
  • 4 blocks
  • Each block is 1 hour, 15 minutes

Each exam is $60 and is available for purchase on the NBME website.

How should I study for the CBSE?

Keep in mind that you’ll be trying to study for the CBSE while still learning new information in your courses. It’s extremely important to keep your coursework as your main priority! Focus on doing as well as you can on your coursework, as it will only help you during your dedicated Step 1 study period. That being said, try to make time each day—even if only 20-30 minutes—to do the following:

  1. Review as many UWorld questions as possible. With each question, make sure to read the answer explanation thoroughly and supplement your learning with the corresponding pages in First Aid. Now is not the time to read First Aid cover-to-cover. Instead, just read short excerpts that apply to the question you are answering.
  2. Select Sketchy videos (Micro, Pharm, +/- Path), if this resource was already helpful for you.
  3. Select Pathoma chapters/videos, if this resource was already helpful for you.
  4. First Aid as a supplement to UWorld questions and new coursework.
  5. Take 1-2 CBSSA exams. You don’t want to take them all, as it’s important to save some for your dedicated Step 1 study period. Be sure to review the test carefully afterwards, as most of your learning will come from your careful review.

When will I receive my NBME CBSE score report?

You should receive an electronic score from NBME within one week of taking the exam.

What do I do with my NBME CBSE exam results?

Like with any NBME Score Report, use the information to create an effective study plan for the real Step 1.

Take a look at your Performance Profile on the Score Report and identify your weakest areas. Plan to set aside about 2-3 hours each day during your dedicated Step 1 study period to focus on these weakest areas, even if the rest of your day is spent looking at other systems or subjects. It’s important to work in daily review of these tough topics.

Once you take your first NBME practice test during your dedicated Step 1 study period, compare the Score Report’s Performance Profile to see if you made any improvements in these troublesome areas. If there are still some areas that are particularly challenging, plan to sprinkle in several days of extra study time to focus on those topics.

The key is to learn and grow from your exam results rather than feel embarrassed or disappointed. This is a learning opportunity that will only make you a stronger test taker on the real exam! Here are some additional tips on how to use your NBME score report.