Methods, systems, and apparatus, including computer programs encoded on computer storage media, for inferring the geographical location of devices. One of the methods includes obtaining device information associated with a first device located at a respective geographical location, the device information including a plurality of events obtained from the first device, wherein least a one event of the obtained events contains ambiguous geographical location information that can be interpreted as relating to one of two or more alternative geographical locations; identifying the at least one event containing ambiguous geographical location information; and determining an estimate of the geographical location of the first device based at least in part on the device information taking into account that the at least one identified event contains ambiguous geographical location information.