What are the subjects in USMLE Step 1?

Questions that are asked in USMLE Step 1 can be grouped into 18 core areas. These areas cover basic concepts and principles of the organ-systems or within individual organ systems. Step 1 of the USMLE covers topics related to traditionally defined disciplines as described in the table below:

Disciplines covered in USMLE Step 1

Anatomy Pathology
Behavioral Sciences Pharmacology
Biochemistry Physiology
Biostatistics and Epidemiology Microbiology

The following interdisciplinary areas are also covered in the USMLE 2018 step 1:

Genetics Aging
Immunology Nutrition
Molecular and Cell Biology
Genetics Aging
Immunology Nutrition
Molecular and Cell Biology


Step 1 classifies test items along two dimensions, system and process.


• 15%–20% General principles
• 60%–70% Individual organ systems (hematopoietic/lymphoreticular, nervous/special senses, skin/connective tissue, musculoskeletal, respiratory, cardiovascular, gastrointestinal, renal/urinary, reproductive, endocrine, immune)
• Biostatistics, epidemiology, and population health


• 10%–15% Normal structure and function
• 55%–60% Abnormal processes
• 15%–20% Principles of therapeutics
• 10%–15% Psychosocial, cultural, occupational, and environmental consideration

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