Guide to the de identification of personal health information Foreword Personal health information comprises the most sensitive and intimate details of ones life such as those relating to ones physical or mental health and the health history of ones family. Intuitively we understand the importance of protecting health information in order to ensure the confidentiality of such personal data and the privacy of the individual to whom it relates. Personal health information must also be accurate complete and accessible to health care practitioners in order to provide individuals with necessary health care. At a broader level for secondary uses that go beyond the treatment of the individual health related data are needed for the benefit of society as a whole. These vitally important secondary uses include activities to improve the quality of care health research and the management of publicly funded health care systems. As the information and privacy commissioner of Ontario Canada my role includes the oversight of health privacy legislation governing the collection use and disclosure of personal health information by organizations and individuals involved in the delivery of health care services. Ontarios Personal Health Information Protection Act (PHIPA) aims to respect an individuals right to privacy in relationship to his or her own personal health information while accommodating the legitimate need to access health information for well defined purposes. PHIPA does this in part by establishing clear rules for the use and disclosure of personal health information for secondary purposes. The object of these rules is to maximize the benefits of both respecting personal privacy and making health information accessible for purposes that serve society as a whole