The thoroughly updated Fourth Edition of this popular and widely used review book offers excellent preparation for the CK (clinical knowledge) component of the USMLE Step 2. This edition contains twenty simulated USMLE tests, totaling 1,000 clinical vignette-based questions, followed by answers and explanations—twelve of these tests are in the book and eight are available online. All vignettes, questions, incorrect answers (distracters), correct answers, and explanations conform to current clinical practice and current USMLE style. Explanations for both correct and incorrect answers are included to help the student understand why (s)he chose an incorrect answer.