This article describes the development of a valid and reliable instrument to measure different dimensions of public trust in health care in the Netherlands. This instrument is needed because the concept was not well developed, or operationalized in earlier research. The new instrument will be used in a research project to monitor trust and to predict behaviour of people such as consulting "alternative practitioners". The idea for the research was suggested by economic research into public trust. In the study, a phased design was used to overcome the operationalization problem. In the first phase, a qualitative study was conducted; and, in the second, a quantitative study. In the first phase, more than 100 people were interviewed to gain insight into the issues they associated with trust. Eight categories of issues that were derived from the interviews were assumed to be possible dimensions of trust. On the basis of these eight categories and the interviews, a questionnaire was developed that was used in the second phase. In this phase, the questionnaire was sent to 1500 members of a consumer panel; the response was 70 percent. The analysis reveals that six of the eight possible dimensions appear in factor analysis. These dimensions are trust in: the patient-focus of health care providers; macro policies level will have no consequences for patients; expertise of health care providers; quality of care; information supply and communication by care providers and the quality of cooperation. The reliability of most scales is higher than 0.8. The validity of the dimensions is assessed by determining the correlation between the scales on the one hand, and people's experience and a general mark they would assign on the other. We conclude that public trust is a multi-dimensional concept, including not only issues that relate to the patient-doctor relationship, but also issues that relate to health care institutions. The instrument appears to be reliable and valid.