We propose planning for a paradigm of context based medicine, in which the basis for making evidence-based medical decisions includes not only traditional published medical knowledge but also evidence from highly processed clinical, environmental, and epidemiological information. Currently, such ambient contextual information is rarely available or at best used only informally by providers and patients making care decisions. The emerging national health information network creates an ideal opportunity for delivering context- appropriate information to decision makers, across institutions and disciplines. The goal of this proposal is to support what the NLM Long Range Plan calls a 21st century intelligent health system. The objective is to support, across Harvard healthcare institutions, inference, diagnosis and clinical prediction by formalizing a digital library infrastructure to facilitate acquisition, processing and delivery of highly processed, usable knowledge from clinical care sites, public health authorities, libraries and patients at home. We will conceptualize and plan a Contextualized Clinical Care Information Resource (C3IR) that links personal, environmental and population data to clinical and personal action by delivering interpreted and tailored information to clinicians through electronic health records and/or personally controlled health records and to individuals through personally controlled health records, at the point of decision. We will ground the planning and development process for this novel library service around four exemplary use cases. Our plan is to build a working model to serve the Harvard Medical community and cohere a learning community of institutional and individual users in the advancement, refinement and development of contextualized evidence based medicine.