This article examines how distrust drives exchange. We propose a theoretical framework integrating the literature of trust into cultural sociology and use a case of patients giving hongbao (red envelopes containing money) to doctors in China to examine how distrust drives different forms of unofficial exchange. Based on more than two years’ ethnography, we found that hongbao exchanges between Chinese patients and doctors were, ironically, bred by the public’s generalized distrust in doctors’ moral ethics. In the absence of institutional assurance, (...) Chinese patients drew on the cultural logic of particularism and its associated cultural repertoire to induce fidelity from their physicians. They mobilized interpersonal networks to function as assurance and presented hongbao as a return of favor to the doctors. This form of exchange is gifting-oriented. Alternatively, if there were no interpersonal networks to rely on, they proactively offered hongbao to doctors at arm’s length in an attempt to personalize the relationship to seek assurance and abate their anxieties. This form of exchange is bribery-oriented. Both forms of exchange co-existed when there was one-way generalized distrust manifested from patients to doctors. When doctors also developed generalized distrust in patients, arm’s length exchanges declined, leaving embedded exchanges as the dominant form. Our study asserts the central role of culture in constituting exchange behaviors and the importance of institutions in shaping the form of exchange. It contributes to the midrange theory of trust, generating a number of hypotheses for future research on the relationships among culture, institutions, distrust, assurance, and illicit exchange. (shrink)