When we began to review the pharmacology material covered in the USMLE Step 1 at the end of our second year at Yale Medical School, we had trouble finding one review source that covered this subject at just the appropriate level. Although we had taken introductory pharmacology during medical school, we found our-selves covering new material as well as reviewing old material from a different angle. Flipping through the highly rated pharmacology review sources, we realized that there was no gold standard review source for this high-yield topic that makes up nearly 20% of USMLE Step 1 questions.Lange Pharmacology Flashcards are the result of our struggles in studying these topics for Step 1 with the particular slant that the boards demand. These cards offer the most complete, concise, and high-yield information for the major drugs tested on Step 1 and in medical school basic science courses. With this fourth edition, we are confident that the content covered in these cards includes the most current and board relevant information that cannot be found in any other single clinical pharmacology review text. To ensure that these cards are high yield, we commissioned two current Yale Medical School student editors to help write this revised edition.We are pleased to present this information in a format modeled after Lange Flashcards: Pathology, our first publication in this series. Each card provides a structured presentation of a specific drug or drug class, and allows students to easily compare and contrast drugs. The introductory cards in each chapter describe the basic principles of that particular drug class that are board relevant and high yield. Each drug-specific card contains a clinical vignette on one side and important characteristics on the reverse side. These characteristics are organized into sections entitled mechanism of action, clinical uses, and side effects. Unlike other review cards on the market, only the information you need to know for the boards are on these cards. If certain drug-drug interactions or routes of administration are high yield, this information is included. Moreover, the most salient features of each drug are highlighted in bold for ease of rapid review.We would suggest using these cards as an adjunct to your pharmacology course in medical school. Being familiar with these cards early on will be very helpful during your Step 1 review. We also encourage you to jot down your own notes in the margins and to make these cards your personal pharmacology review for the boards.We are confident that the fourth edition of Lange Pharmacology Flashcards will be one of the most powerful tools to help prepare you for the boards and will serve as a resource that will bridge your basic science knowledge with the clinical aspects of disease. We wish you the best of luck on Step 1, and welcome your comments on how to improve this study tool in the next edition.