Disclosed is a communicatory navigation system including an information center (150), at least one navigation unit (100) each mounted on a vehicle and communication means for allowing bi-directional data communication between the information center and the navigation unit. Data transmission from the navigation unit to the information center is made during a period of communication that begins when the navigation unit become communicatable with the information center and ends when the bi-directional data communication therebetween is disconnected. The navigation unit is provided with a drive route history memory area (131) and an instrument operation history memory area (132), and data in these memory areas are transmitted to the information center, together with the vehicle current position data and the destination position data. The information center determines a recommended drive route from the current position to the destination, not only with reference to its own database (158) but also taking into consideration the history data. For example, if it is determined that there is a traffic accident or heavy traffic jam in some route, a bypass route is determined and transmitted back to the navigation unit. When the previous drive route indicated by data in area (131) is not found in the database (158), it can be recognized as a newly constructed road for inclusion in the database.