The philosopher Henry Richardson's short book is a defense of a position on a neglected topic in medical research ethics. Clinical research ethics has been a longstanding area of study, dating back to the aftermath of the Nazi death-camp doctors and the Tuskegee syphilis study. Most ethical regulations and institutions (such as Institutional Review Boards) have developed in response to those past abuses, including the stress on obtaining informed consent from the subject. Richardson points out that that these ethical regulations do not address one of the key dilemmas faced by medical researchers -- whether or not they have obligations towards subjects who need care not directly related to the purpose of the study, termed 'ancillary care obligations'. Does a researcher testing an HIV vaccine in Africa have an obligation to provide anti-retrovirals to those who become HIV positive during the trial? Should a researcher studying a volunteer's brain scan, who sees a possible tumor, do more than simply refer him or her to a specialist? While most would agree that some special obligation does exist in these cases, what is the basis of this obligation, and what are its limits? Richardson's analysis of those key questions and the development of his own position are at the heart of this book, which will appeal to bioethicists studying research ethics, to policy makers, and to political and moral philosophers interested in the obligations of beneficence, one of the key issues in moral theory.