In this thesis I examine the medical concept of informed consent and the philosophical concept of autonomy in conjunction with the relationship between them. This examination is complicated because autonomy can refer to decisions or persons. Further autonomy may have instrumental or intrinsic value. These differences mean autonomy may be respected in different ways. This examination is further complicated because whilst a vast wealth of medical literature exists on informed consent and mentions autonomy, very little of this literature does more than mention autonomy. As a result of my examination I argue for the following. Firstly I argue the form of autonomy underlying informed consent should be personal autonomy and to respect autonomy means accepting autonomous decisions. Secondly I show in certain contexts a surrogate decision maker cannot make a decision on behalf of an incompetent patient that would be generally agreed to be in his best interests. I will argue in such contexts a patient's decision should always be accepted as the concept of competence becomes detached from the concept of informed consent. Thirdly I show a patient may make an autonomous decision based only on understanding the purpose of the procedure he is consenting to. I will argue it follows a patient should not be required to understand details of the nature of the procedure he is consenting to for his consent to be accepted. Fourthly I argue an autonomous decision must be one an agent identifies with and has some persistence. I will show these conditions are satisfied by an autonomous agent's absence of restlessness to change his decision Lastly I argue informed consent decisions should be linked to a patient's ability to understand the risk involved in his decision and not directly linked to the degree of risk involved in his decision.