Abstract
Research involving the vulnerable sick raises difficult challenges for investigators and Institutional Review Boards. Exactly who among the ill counts as vulnerable is a matter of judgement, and involves consideration of susceptibility to harm and capacity to provide free and informed consent. A balanced approach is required when protections are considered, and the benefits as well as the risks of research participation must be carefully weighed. A variety of protections for the vulnerable sick in research are available, including enrolling subjects in a study only with a strong justification, ensuring that consent is free and comprehending, and setting limits on the risk to which they may be asked to endure. Discussion of three contemporary controversies, placebo‐controlled trials in the psychiatric setting, phase I clinical trials and oncology patients, and emergency room research involving patients incapable of giving consent, highlights the little recognized prominence of risk‐benefit issues in the clinical studies in the vulnerable sick.