Updating data between the mobile devices belonging to a given user group is shown. In a mobile device (301, 302), there can be recorded information (406) of the members of a given user group, and a connection can be established from the device (301, 302) to other devices (303, 304, 401) of the user group members. In addition, the device includes means for defining the changing information as update data (407) related to said user group, and means for transmitting (303, 304, 401) the update data automatically to each device belonging to the user group through a defined connection bus. The device also includes means for receiving (303, 304, 401) the data defined to be updated, and means for saving (406, 407) the received update data in the device.