In this fast-moving age of data banking, data are a currency, and often a commodity. Electronic health records are being developed everywhere. Increasingly, data collected for various primary purposes are being re-used for research. With personal mobility, contracting of services, and telemedicine, health care data are crossing national borders, and therefore so are genetic information, biological materials, and reimbursement data. There is much public and legal concern about the implications. This article addresses the question: Under what conditions may data not collected specifically for research, such as primary medical data, be re-used for health research without compromising the privacy of the data-subjects?