In order to meet an increasing demand for a standard file format which would facilitate the exchange of image files from one computer to another, the protocol initiated by Report #10 of the American Association of Physicists in Medicine has been adopted. This protocol uses the concept of an ASCII file in which key-value pairs are used to describe the various parameters of the image file. Keys specific to nuclear medicine image files have been established and are published here. In addition, the latest version of the keys has been placed on a list server which is accessible by electronic mail. This will facilitate the development of conversion programs which will also be placed on the same list server as they become available.