Thoracic outlet syndrome (TOS) describes a group of disorders in the upper extremity and neck where vasculature and nervous structures are compressed, leading to symptoms of poor circulation, paresthesia, pain and weakness. TOS has a variety of types including neurogenic and vascular TOS and is difficult to diagnose because of many conditions that mimic it. Treatment of TOS is based on decompressing the structures that are restricting the nerves and vessels in the thoracic outlet. Approaches include physical therapy and surgery, which will be discussed in this course. It is important for Physical Therapists and Physical Therapist Assistants to comprehensively manage patients with TOS because it is a common condition. Therapists should recognize TOS as a condition, refer when patients are not improving and intervene appropriately and efficiently with manual therapy, exercise, education and modalities. This course will describe thoracic outlet syndrome in detail including clinical presentation, most effective treatments and case studies to challenge clinical reasoning.