This paper focuses on constructions of research ethics by primary care physicians in the USA as they engage in contract research for the pharmaceutical industry. Drawing first on historical studies of physicians as investigators and then on 12 months of qualitative fieldwork in the Southwestern US, this paper analyzes the shifting, contextualized ethics that shape physicians’ relationships with patients/subjects and pharmaceutical companies. Just as physicians followed professional codes of ethics prior to the codification of acceptable research conduct in the 1980s, physicians today continue to develop tacit systems of research ethics. This paper argues that private-sector physicians primarily conceptualize their ethical conduct in relation to the pharmaceutical companies hiring them, not to human subjects they enroll in clinical trials. This is not to say that these physicians do not follow the formal U.S. regulation to protect human subjects, but rather that their financial relationships with the pharmaceutical industry have a greater influence on their identities as researchers and on their constructions of their ethical responsibilities.