This is a practical manual for clinicians who take care of patients with concussions. The long-term effects of concussions are an increasingly recognized problem in the medical community and by the general public. Most people recover well from concussions, but a substantial minority does not. However, most clinicians do not have specific training in how to evaluate and treat concussion patients who do not make a rapid and complete recovery. This manual, based on the experience of the director of the concussion clinic at Washington University in St Louis, provides specific step-by-step guidance for managing a variety of problems related to complex concussions: making an accurate diagnosis, general treatment strategies, headaches, sleep disruption, attention deficit, mood instability, anxiety and depression, post-traumatic stress, personality change, balance problems, dizziness, fatigue etc. Furthermore, there are specific sections on return to work, return to driving, return to school and return to contact sports. Finally, the manual includes information on special topics, such as concussion in adolescents, children, contact sport athletes, military personnel, and patients involved in medico-legal matters. The manual is written for clinicians with a broad range of backgrounds: primary care physicians, nurse practitioners, physicians assistants, athletic trainers, emergency medicine doctors, neurologists, neurosurgeons, psychiatrists, and rehabilitation medicine physicians should all be able to use the manual effectively. There is information on how to set up a specialty concussion clinic, and an extensive list of internet-based resources related to concussion. A list of other publications is provided to point to additional detailed information beyond what a pocket-sized on-the-fly manual can provide.