Step 2 CS (Clinical Skills)

The clinical skills examination is a separately administered component of Step 2 and is referred to as Step 2 Clinical Skills, or Step 2 CS. The computer-based, multiple-choice component of Step 2 is referred to as Step 2 Clinical Knowledge, or Step 2 CK. USMLE Step 2 CS is administered at five regional test centers (CSEC Centers) in the United States.

Sources: http://www.usmleworldwide.com/blog/?p=62