What are the top 20 most frequently tested principles on the United States Medical Licensing Examination (USMLE) Step 1 exam?

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Last updated: March 7, 2025View editorial policy

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From the Research

The top 20 most highly tested principles on the USMLE Step 1 exam include fundamental concepts that span multiple disciplines, such as biochemical pathways, pharmacology, microbiology, pathology, immunology, neuroanatomy, genetics, physiology, embryology, cell biology, biostatistics, and epidemiology. These principles are tested because they represent the scientific foundation of medicine and demonstrate a student's ability to apply basic science concepts to clinical scenarios, which is essential for clinical reasoning and patient care 1. Some of the key concepts that are consistently tested include:

  • Biochemical pathways like glycolysis and the Krebs cycle
  • Pharmacology principles such as drug mechanisms of action, pharmacokinetics, and dose-response relationships
  • Microbiology concepts including bacterial classification, virulence factors, and antibiotic mechanisms
  • Pathology principles covering inflammation, neoplasia, and cell injury
  • Immunology concepts like T and B cell function, cytokine signaling, and hypersensitivity reactions
  • Neuroanatomy principles, particularly regarding brain lesions and pathway disruptions
  • Genetics topics including inheritance patterns, mutations, and genetic disorders
  • Physiology principles covering cardiovascular, respiratory, renal, and endocrine systems
  • Embryology concepts, especially regarding developmental anomalies
  • Cell biology principles including cell signaling, apoptosis, and the cell cycle
  • Biostatistics and epidemiology concepts including study design, statistical significance, and disease measures It's worth noting that while the USMLE Step 1 exam is transitioning to a pass/fail system, the content and principles tested will remain the same, and students should continue to focus on mastering these fundamental concepts 2. Additionally, studies have shown that USMLE Step 1 scores are moderately correlated with clinical performance, and that students who use interactive study resources such as question banks tend to perform better on the exam 3, 4. Overall, mastering the top 20 most highly tested principles on the USMLE Step 1 exam is crucial for medical students to demonstrate their knowledge and application of basic science concepts, and to prepare for a successful career in medicine.

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