BACKGROUND: The financial burden of medical care expenses is increasing for American families. However, the association between high medical cost burdens and patient trust in physicians is not known. OBJECTIVE: To examine the association between high medical cost burdens and self-reported measures of patient trust and perceived quality of care. METHODS: Cross-sectional household survey based on random-digit dialing and conducted largely by telephone, supplemented by in-person interviews of households with no telephones. The sample for this analysis includes 32,210 adults who reported having a physician as their regular source of care. Measures of patient trust include overall trust, confidence in being referred to a specialist, and belief that the physician uses more services than necessary. Perceived quality measures include thoroughness of exam, ability to listen, and ability to explain. RESULTS: In adjusted analyses, persons with high medical cost burdens had greater odds of lacking trust in their physician to put their needs above all else (OR = 1.43, CI = 1.19, 1.73), not referring them to specialists (OR = 1.39, CI = 1.22, 1.58), and performing unnecessary tests (OR = 1.42, CI = 1.20, 1.62). Patients with high medical cost burdens also had more negative assessments of the thoroughness of care they receive from their physician (OR = 1.26, CI = 1.02, 1.56). The association of high medical cost burdens with patient trust and perceived quality of care was greatest for privately insured persons. CONCLUSION: The rising cost of medical care threatens a vital aspect of the effective delivery of medical care-patient trust in their physician and continuity of care. Exposing patients to more of the costs could lead to greater skepticism and less trust of physicians' decision-making, thereby making health-care delivery less effective.