The discussion is based on the experience of the Centro Solidarieta di Modena in Modena, Italy. An information system must keep information usable and easily accessible to avoid the fragmentation of services and to communicate efficiently with other services in contact with the same client. This needs to be done without creating additional work for the staff. A well-planned database can account for frequent treatment breaks and resulting breaks in data continuity while documenting the center's therapeutic experiences. The interview and form should collect the smallest pieces of information possible both to enhance the objectivity of answers and to facilitate the observation of the interactions between sets of items. The Centro Solidarieta di Modena uses software called Biography Writer to produce a biography in everyday language using the data collected in the interview. Periodic research uses the data to define drug users' main needs, compare the center with other services, and other purposes. The database is one of the first attempts to use the nonsequential data processing system called Artificial Neural Network. Figures, author biographies and photographs, and 8 references (Author abstract modified)