Clinical reasoning can be defined as thinking through the various aspects of patient care to arrive at a reasonable decision regarding the prevention, diagnosis, or treatment of a clinical problem in a specific patient. Patient care includes history taking, conducting a physical exam, ordering laboratory tests and diagnostic procedures, designing safe and effective treatment regimens or preventive strategies, and providing patient education and counseling. Obviously, the clinician should be well grounded in biomedical and clinical sciences and skillful at gathering clinical data from a patient before engaging in the process of clinical reasoning. This guide does not address the knowledge and skills required to competently gather and interpret clinical data. Rather, the guide is intended to help clinicians take the next step, which is determining the best course of action to take based on what is known or what can reasonably be hypothesized from clinical data. So, it isn't enough to have a strong background in the biomedical sciences or to possess excellent clinical knowledge, nor to know how to conduct a history and physical exam on a patient, or even to know how to formulate a differential diagnosis given the signs, symptoms, and test results of a patient. n addition to all of this, there is still a need to think critically about all the important information pertaining to a particular case and to formulate or synthesize a rational plan of action. In short, clinical reasoning requires critical thinking skills, abilities and traits which are often not taught in schools and colleges for the health professions. This guide focuses on a framework for critical thinking relevant to all domains of human thought and is specifically focused on clinical reasoning. The suggestions and conclusions herein are consistent with the suggestions and conclusions found in the works of prominent thinkers in the clinical fields.