At the Paul Scherrer Institute the High Intensity Proton Accelerator (HIPA) as well as the new biomedical facility (PROSCAN) use an in-house developed Control system called ACS. The SLS and future XFEL on the other hand use EPICS. In view of the standardization of software and hardware equipment, the decision was made to replace the ACS system with EPICS. Two years ago we started the migration of the PROSCAN control system, which has already from the beginning been built with a high degree of hardware standardization, using VME components only. The migration was finished at the end of last year, but we did not perform the definitive switch over due to a biomedical application that still has to be adapted by their authors. In the coming years we also expect to migrate the ACS control system of the high intensity proton accelerator to EPICS, taking advantage of the work and experience we gained with the PROSCAN migration. We will present here the goals that have been followed and the way we proceeded for the very successful migration of the PROSCAN control system.