During recent decades the doctrine of informed consent has become a standard part of medical care as an expression of patients' rights to self-determination. In situations when only one treatment alternative exists for a potential cure, the extent of a patient's self-determination is constrained. Our hypothesis is that for patients considering a life-saving procedure such as bone marrow transplant (BMT), informed consent has little meaning as a basis for their right to self-determination. A longitudinal study of BMT patients was undertaken with four self-administered questionnaires. Questions centered around expectations, knowledge, anxiety and factors contributing to their decision to undergo treatment. Although the informed consent process made patients more knowledgeable about the treatment, their decision to consent was largely based on positive outcome expectations and on trust in the physician. Informed consent relieved their anxieties and increased their hopes for survival. Our conclusion was that the greatest value of the informed consent process lay in meeting the patients' emotional rather than cognitive needs. When their survival is at stake and BMT represents their only option, the patient's vulnerability puts a moral responsibility on the physician to respect the principle of beneficence while not sacrificing the patient's right to self-determination.