A computer-based system and method is disclosed which constructs medical histories by direct interactions between the patient and system that acquires pertinent and relevant medical information covering the complete life of a given patient. The system and method insure that a complete life long medical history is acquired from every patient interacting with the health care system. Once acquired, the facts of the patient's life long and family medical history are analyzed automatically by databases to generate a set of the most reasonable diagnostic possibilities (the differential diagnosis) for each medical problem identified and for each risk factor for disease that is uncovered in the historical database. Further, the automatically analyzed database of historical medical information is used as the search tool for bringing to bear, on the diagnosis and treatment of each medical problem identified in each patient, the entirety of medical knowledge that relates to and can be useful for the correct and efficient diagnosis and treatment of each of every patient's medical problems. This collection of information is analyzed to generate a final diagnosis and treatment regimen.