100+ Free NBME CBSSA Practice Questions
Pass your NBME Comprehensive Basic Science Self-Assessment exam on the first try — instant access, no signup required.
A 10-year-old boy has a family history of early colon cancer. Genetic testing shows a germline mismatch repair mutation. Which molecular finding is expected in his tumors?
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Key Facts: NBME CBSSA Exam
200
Official Form Questions
NBME CBSSA page
4
Official Sections
NBME CBSSA page
75 min
Standard-Paced Section Time
NBME CBSSA page
5 h
Self-Paced Section Time
NBME CBSSA page
7
Available Forms Listed
NBME CBSSA page
$62
Official Form Price Listed
NBME CBSSA page
100
Free Practice Questions Here
Open Exam Prep
NBME CBSSA is the official Comprehensive Basic Science Self-Assessment for students preparing for USMLE Step 1. NBME lists seven available forms, each with four 50-question sections in standard-paced mode. This free bank provides 100 original CBSSA-style items focused on mechanism-driven basic science reasoning rather than copied or recalled official questions.
Sample NBME CBSSA Practice Questions
Try these sample questions to test your NBME CBSSA exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1A 23-year-old man develops dark urine and back pain 2 days after taking primaquine for malaria prophylaxis. Peripheral smear shows bite cells and Heinz bodies. Which biochemical abnormality most directly explains this reaction?
2A newborn has bilious vomiting during the first day of life. Radiography shows air in the stomach and proximal duodenum with no distal bowel gas. Which embryologic process failed?
3A 55-year-old man with exertional chest pressure has a fixed narrowing of the left anterior descending artery. During exercise, which local metabolic change primarily increases blood flow to the ischemic myocardium distal to the stenosis?
4A 7-year-old boy has recurrent skin abscesses and pneumonia caused by Staphylococcus aureus. Neutrophils fail to reduce nitroblue tetrazolium after stimulation. Which organism would create a similar clinical risk because it is catalase positive?
5A 49-year-old woman has episodic burning pain in her hands and feet with redness. Laboratory studies show platelets of 950,000/mm3 and a JAK2 mutation. Which mechanism best explains her painful episodes?
6A 64-year-old man with benign prostatic hyperplasia develops dizziness when standing after starting tamsulosin. The drug most directly relaxes smooth muscle by blocking which receptor?
7A screening test for a cancer has 95% sensitivity and 80% specificity. In a population where disease prevalence decreases substantially, which test characteristic will decrease most directly?
8A 4-year-old boy has severe recurrent sinopulmonary infections. Flow cytometry shows absent mature B cells with normal T-cell counts. His maternal uncle had similar infections. Which gene product is most likely defective?
9A 38-year-old woman with ulcerative colitis has progressive jaundice and pruritus. Cholangiography shows multifocal strictures and dilation of intrahepatic and extrahepatic bile ducts. Which pathologic process is most likely?
10A 6-month-old infant has recurrent vomiting, seizures, lactic acidosis, and failure to thrive. Serum alanine is elevated. Which enzyme complex is most likely deficient?
About the NBME CBSSA Exam
The NBME Comprehensive Basic Science Self-Assessment is a Step 1 readiness tool that tests integrated basic science content through clinical vignettes. Official CBSSA score reports emphasize equated percent correct performance, content-area feedback, longitudinal performance, answer rationales, and an estimated probability of passing USMLE Step 1.
Assessment
Free 100-question practice bank modeled on Step 1 basic science reasoning; official CBSSA forms use four 50-question sections
Time Limit
Official standard-paced CBSSA: 4 sections x 1 hour 15 minutes; self-paced: 5 hours per section
Passing Score
No CBSSA pass score; reports estimate Step 1 passing probability
Exam Fee
$62 per official form listed by NBME (National Board of Medical Examiners (NBME))
NBME CBSSA Exam Content Outline
Pathology
Cell injury, inflammation, hemodynamics, neoplasia, and organ-system disease mechanisms.
Physiology
Cardiovascular, renal, respiratory, endocrine, gastrointestinal, and neurophysiology mechanisms.
Microbiology and Immunology
Pathogens, vaccines, immune cells, antibodies, complement, hypersensitivity, and immune deficiency.
Biochemistry and Nutrition
Enzymes, metabolism, vitamins, molecular biology, nutrition, and inherited metabolic disorders.
Pharmacology
Drug mechanisms, toxicities, autonomic effects, chemotherapy, antimicrobials, and pharmacokinetics.
Gross Anatomy and Embryology
Anatomic lesions, nerve injury, congenital defects, vascular supply, and embryologic origins.
Behavioral Sciences
Ethics, communication, study design, bias, screening tests, and population-health interpretation.
Histology and Cell Biology
Cellular organization, organelles, epithelial and connective tissue, signaling, and microscopy.
Genetics
Inheritance, imprinting, repeat expansion, population genetics, and mutation mechanisms.
How to Pass the NBME CBSSA Exam
What You Need to Know
- Passing score: No CBSSA pass score; reports estimate Step 1 passing probability
- Assessment: Free 100-question practice bank modeled on Step 1 basic science reasoning; official CBSSA forms use four 50-question sections
- Time limit: Official standard-paced CBSSA: 4 sections x 1 hour 15 minutes; self-paced: 5 hours per section
- Exam fee: $62 per official form listed by NBME
Keys to Passing
- Complete 500+ practice questions
- Score 80%+ consistently before scheduling
- Focus on highest-weighted sections
- Use our AI tutor for tough concepts
NBME CBSSA Study Tips from Top Performers
Frequently Asked Questions
What is the NBME CBSSA?
CBSSA stands for Comprehensive Basic Science Self-Assessment. It is NBME's self-assessment for students preparing for USMLE Step 1 and is designed to gauge basic science readiness.
How many questions are on an official CBSSA form?
NBME describes the standard-paced CBSSA as four sections of 50 questions each, for 200 questions per official form.
How is CBSSA timed?
The official standard-paced option allows 1 hour and 15 minutes per 50-question section. NBME also lists a self-paced option with 5 hours per section.
Does CBSSA give a Step 1 passing prediction?
NBME reports an estimated probability of passing USMLE Step 1, along with equated percent correct scores and content-area feedback. The estimate is not a guarantee of future Step 1 performance.
Are these questions copied from NBME forms?
No. This bank contains original educational questions written to practice the same basic science reasoning style without reproducing official, recalled, or copyrighted NBME items.
What should I review after a CBSSA-style block?
Review the mechanism behind each missed item, then group misses by discipline and system. CBSSA readiness depends on integrating pathology, physiology, pharmacology, microbiology, biochemistry, genetics, anatomy, and biostatistics.