We designed a general-purpose computer program, Osiris, for the display, manipulation, and analysis of digital medical images. The program offers an intuitive, window-based interface with direct access to generic tools. Characterized by user-friendliness, portability, and extensibility, Osiris is compatible with both Unix-based and Macintosh-based platforms. It is readily modified and can be used to develop new tools. It is able to monitor the entries made during a work session and thus provide data on its use. Osiris and its source code are being distributed, free of charge, to universities and research groups around the world.