The OSIRIS software has been designed as a general medical image manipulation and analysis software. The design is mainly based on the following criteria: portability, extendibility and suitability for any imaging modality. OSIRIS is designed to deal with images provided by any type of digital imaging modality to allow physicians to easily display and manipulate images from different imaging sources using a single generic software program. Portability ensures the software implementation on different types of computers and workstations. Thus, the user can work in the same way, with exactly the same graphical user interface, on different stations. Also by supporting standard file formats, the OSIRIS software provides access to images from any imaging modality. The OSIRIS program was developed as part of the Geneva PACS project and is intended for physicians and non computer-oriented users allowing them to display and manipulate medical images. Its standard original version included only basic image manipulation tools accessible through a convenient and user-friendly graphic interface. In addition to being used at the University Hospital of Geneva, it was widely distributed around the world and was adjusted according to user's comments and suggestions. This program was also designed to serve as a development of more advanced image processing and analysis tools.