We have implemented a structured reporting system for medical imaging that replaces dictation and transcription by allowing radiologists and other imaging professionals to select imaging findings from medical lexicons. The system uses an imaging-specific information model called a Description Set to organize selected terms in a relational database. The system's expressiveness for reporting is enhanced by its ability to codify uncertainty about imaging observations and to represent explicit causal and associational relationships among imaging findings. The system promptly and automatically generates a text report that referring physicians are accustomed to receiving. Because the image report information is stored in a fully coded fashion, it can be used to provide real-time decision support to radiologists, to transmit coded imaging data to electronic patient record systems, to measure and improve radiologists' performance, and to index images by content.