This paper proposes an ethical reflection on personalized medicine and more precisely on the diagnostic technology underlying it, including nanochips. Our approach is inspired by a combination of two philosophical frames of reference: first, John Dewey’s distinction between intuitive valuation and reflexive evaluation, second, John Rawls’ reflective equilibrium. We aim at what we call a ‘reflexive equilibrium’, a mutual adjustment between on the one hand, the intuitive beliefs scientists have about the ethics of the technologies they work on (‘valuations’ in (...) Dewey’s vocabulary) and, on the other hand, the reflexive ethical assessment of these technologies (‘evaluations’). Our goal, in this paper, is to provide the first step of this process through a philosophical analysis of some valuations on individualized medicine. In order to apprehend the ethical values shaping the development of biochips, we present and analyze qualitative interviews with scientists involved in the conception and the development of biochips involving nanotechnologies. We then propose a critical assessment of the role of ethics in these scientific practices. Last, we suggest two distinct and complementary ways to solve some of the issues brought to light by the interviews, without aiming at any dogmatic or “ready-made” answer. The first of these perspectives gives a central role to the capability individuals could achieve through personalized medicine; the second approach analyses the ethical disruptions entailed by personalized medicine with a special focus on care. (shrink)