OpenMRS is a software platform and a reference application that enables design of a customized medical records system (MRS). It is a common platform upon which health informatics and eHealth efforts in low-income countries can be built. OpenMRS is based on the principle that information should be stored in a way that makes it easy to summarize and analyze (i.e., minimal use of free text and maximum use of coded information). At its core is a concept dictionary that stores all diagnoses, tests, procedures, drugs, and other general questions and potential answers. The OpenMRS system works in more than 3,000 medical sites for about 8.7 million patients in more than 64 countries.