A Roadmap For Geant4

The Geant4 simulation toolkit is now in the 14th year of its production phase. Geant4 is the choice of most current and near future high energy physics experiments as their simulation engine, and it is also widely used in astrophysics, space engineering, medicine and industrial application domains. Geant4 is a "living" code under continuous development; improvement of physics quality and computational speed is still a priority for Geant4. It is evolving and being enriched with new functionalities. On the other hand, the simulation paradigm that prevailed during the foundation of Geant4 is now being rethought because of new technologies in both computer hardware and software. The Geant4 Collaboration has identified many options and possibilities. Geant4 has accommodated some of these by providing a multi-threading prototype based on event-level parallelism. In this article we discuss the past, present and future of the Geant4 toolkit.