Early clinical trials for new anti-cancer drug treatments typically use patients with cancer as research subjects. This paper identifies some of the ethical and practical concerns that arise from the recruitment of a vulnerable group of patients and their exposure to a drug of unknown risk or benefit. This review discusses the ethical principles related to recruitment and informed consent in cancer trials, and indicates that there is a lack of consensus concerning the requirements, process and practice of informed consent. It is suggested that, as yet, little is known about patients' decision making framework in this situation, and the need for further work that concentrates on the patient's point of view is highlighted. The paper concludes by discussing some of the difficulties associated with obtaining patients' opinions, and suggests that the use of a qualitative approach may overcome some of these problems.