Overview of Geant4 applications in medical physics

We present a series of achievements associated with Geant4-based applications in medical physics and, in particular, in radiotherapy (external beams and brachytherapy), protontherapy, PEM, PET, MRT, metabolic therapy, IORT; projects in microdosimetry and radiobiology are beginning. The Geant4 CT-interface allows to reproduce realistically the patient anatomy, the integration to the GRID allows to run the applications sharing distributed computing resources. The Geant4 Medical Physics Group has born from the collaboration of Geant4 with several research and medical physics institutes in Europe.