TRUST IS FUNDAMENTAL in health research, yet there is little empirical evidence that explores the meaning of trust from the perspective of human subjects. The analysis presented here focuses on how human subjects talked about trust in the in-depth interviews. It emerged from the accounts that trust could not be assumed in the research setting, rather it was portrayed as a dynamic concept, built and easily broken, characterized by reciprocity and negotiation. Human subjects were ambivalent about who, when, what, and how much to trust in the research endeavor. This paper adds a fresh perspective to the literature on trust, and so offers a currently neglected, and little understood dimension to the discourse around health research ethics.