INTRODUCTION:Previous studies have measured individuals' willingness to share personal information stored in electronic health records (EHRs) with health care providers, but none has measured preferences among patients when they are allowed to determine the parameters of provider access. METHODS: Patients were given the ability to control access by doctors, nurses, and other staff in a primary care clinic to personal information stored in an EHR. Patients could restrict access to all personal data or to specific types of sensitive information, and could restrict access for a specific time period. Patients also completed a survey regarding their understanding of and opinions regarding the process. RESULTS: Of 139 eligible patients who were approached, 105 (75.5 %) were enrolled, and preferences were collected from all 105 (100 %). Sixty patients (57 %) did not restrict access for any providers. Of the 45 patients (43 %) who chose to limit the access of at least one provider, 36 restricted access only to all personal information in the EHR, while nine restricted access of some providers to a subset of the their personal information. Thirty-four (32.3 %) patients blocked access to all personal information by all doctors, nurses, and/or other staff, 26 (24.8 %) blocked access by all doctors and/or nurses, and five (4.8 %) denied access to all doctors, nurses, and staff. CONCLUSIONS: A significant minority of patients chose to restrict access by their primary care providers to personal information contained in an EHR, and few chose to restrict access to specific types of information. More research is needed to identify patient goals and understanding of the implications when facing decisions of this sort, and to identify the impact of patient education regarding information contained in EHRs and their use in the clinical care setting.