In a treatment process, a doctor has to view a lot of medical data about symptoms, test results, drugs and their dosages in a period of time. It is convenient for the doctor to view and search for any information he/she needs if all the medical data of each patient are visualized appropriately. For that purpose, we propose EMRVisualization, an electronic medical record visualization system, to visualize all the related medical data in an integrative manner. The system provides an interactive visualization with accurate data at different detail levels, quick access and convenience for a doctor to track the progress of each patient over time. Its development is detailed in this paper. Its demonstration with the real data of gastroenterological Vietnamese patients in Thong Nhat Hospital, Ho Chi Minh City, Vietnam, is conducted. It also shows that every interaction of a doctor can be accomplished in at most two steps.