United States Medical Licensing Examination (USMLE) Step 1. USMLE Step 1 International: 300 MCQs. 2026-2027 International Edition: Practice Questions with Answers and Explanations. USMLE Step 1 Biochemistry and Molecular Genetics. USMLE Step 1 Cell Biology and Basic Histology. USMLE Step 1 Immunology and Infectious Diseases. USMLE Step 1 General Pathology and Mechanisms of Disease. USMLE Step 1 General and Systemic Pharmacology. USMLE Step 1 Cardiovascular and Pulmonary Systems.