Abstract: Although candor with a physician has long been known to contribute to the health of the individual and, ultimately, of the society at large, recent trends in the generation and collection, storage, manipulation, use, and transfer of information---including patients' medical information---may be undermining the public's expectations of confidentiality. These diminished confidentiality expectations may in turn motivate individuals to withhold sensitive information from their health-care providers or even to avoid their care altogether. This study relied on expectancy theory to investigate (1) the relationship between respondents' willingness to disclose personal information to a health-care provider and their expectations concerning the confidentiality accorded to that information and (2) their expectations of any other positive or negative consequences of the disclosure. It also tested a methodology previously untried in this arena. A purposefully chosen sample of 430 respondents with widely varied demographic characteristics completed a self-administered written questionnaire based largely on a series of vignettes, each of which described a fictional situation between a doctor and a patient and involving sensitive medical conditions and the disclosure of equally sensitive personal facts. The researcher used content and correlational analyses and analyses of variance (ANOVAS) to identify patterns of association in the data. These analyses revealed a statistically significant relationship between respondents' confidentiality expectations and their willingness to disclose. Within the sample, this relationship was significantly stronger for men than for women. The findings suggest that certain other demographic traits may also play a role in the strength of the relationship. Also, while diagnosis and/or treatment was the most commonly cited consideration in deciding whether to disclose, many other incentives or disincentives also appeared to be at work. The study's findings provide support for part of a previously untested behavioral model applying expectancy theory to the privacy domain. It also identifies demographic variables that should be examined further and contributes operationalizations for constructs that have proved elusive in the past. Finally, the study's results hold several implications for public policy vis-à-vis medical confidentiality.