Our hospital acts as a regional core hospital through inter-hospital collaboration. Geographical information is necessary to guide patients to the other hospitals. Although paper maps, which contain directions, nearest public transportation, etc., are usually provided to guide patients to the hospitals, the geographical information tends to change daily. However, updating the geographical information on the maps is costly. We constructed an electronic geographical information system using the Google Map API ( http://code.google.com/apis/maps/ ) with open source software to improve our ability to collaborate with other clinics.