This chapter provides an evidence-based and practical overview of informed consent for neurological clinical trials. The purpose of research is fundamentally different from that of treatment. When a surgeon recommends an operation to her patient, the patient can reasonably assume that the surgeon's primary purpose in recommending the procedure is to improve his health and welfare. In order for a person to provide valid, informed consent, three conditions must be met. The person must be provided adequate information. He or she must possess decision-making capacity. The decision must be made voluntarily, without coercion or undue influence. In practice, close family members tend to serve as de facto surrogates. Although the concept of therapeutic misconception (TM) seems intuitive, the term is used in the literature to denote a number of related, but not always identical concepts.