Informed choice of health insurance could morally justify later, potentially harmful rationing decisions the way informed consent justifies potentially harmful medical interventions. In complex and technical areas, however, individuals may base decisions more on trust than informed choice. We interviewed enrollees in managed care plans in Southeast Michigan, United States, to explore in detail their expectations and experiences in choosing and using their health plan. Diverse subjects participated in semi-structured interviews about health insurance choices, experiences, and expectations. Results are presented for the theme of trust (and distrust), which emerged spontaneously in discussions about health care and health insurance. Forty subjects diverse in age, ethnicity, and income took part in 31 interviews. Interviewees mentioned many of the elements of interpersonal trust in specific physicians, often in the context of discussions about care experiences, doctor payment, and conflict of interest. Elements included physical and emotional vulnerability, expectations of goodwill, advocacy and competence. and belief in professional ethics. Trust in the medical profession had more hesitancy, and often included mention of honesty or ethics. Elements of trust in hospitals included vulnerability to financial loss, and expectations of competence (quality). Elements of trust in health insurance plans often emerged in discussions about catastrophic illness coverage denials, and profit, and were more often negative. Vulnerability, worry, fear and security were prominent. Fiscal rather than clinical competence was emphasized, while expectations of goodwill remained. Enrollees in managed care plans spontaneously discussed trust and distrust in individuals and institutions during conversations about their insurance expectations and experiences. Similarities and differences in the elements and the context of these discussions illuminate distinctions between these healthcare relationships of trust.