In order to become a licensed physician in the United States one must pass all 3 USMLE Steps. USMLE Step 2 CK is the second of the 3 examinations you must pass. Technically there are 4 exams you have to pass because the USMLE Step 2 is composed of the USMLE Step 2 CK and USMLE Step 2 CS. The 445 page First Aid study guide for the USMLE Step 2 CK is filled with lots of resources for you to help you ace that exam!