Geant4 is a toolkit for the simulation of particles passing through and interacting with matter. Its areas of application include high energy, nuclear and accelerator physics, as well as studies in medical and space science. Geant4 is developed and maintained by the international Geant4 Collaboration. Members of the SLAC Geant4 team have been actively participating in the Geant4 collaboration since its beginning, and currently take leading roles in several key areas of the collaboration. SLAC Geant4 members made significant contributions in simulation development for the BaBar experiment at SLAC, which pioneered the use of Geant4 in the simulation of high energy physics experiments. The SLAC Geant4 Team supports the use of Geant4 for on-site users including ATLAS, BaBar, Cryogenic Dark Matter Search (CDMS), Enriched Xenon Observatory (EXO), Fermi Gamma-ray Space Telescope, and International Linear Collider. The team also supports general Geant4 users of all application domains in North America and beyond.