The present article describes an ambitious research project being conducted jointly by EDF, HQ and EPFL, with the aim of developing a method suitable for industrial use for predicting cavitation in Francis turbines on the basis of scale model testing. Results concerning the notion of erosion aggressiveness, methods to measure it -accelerometer, pressure fluctuations and pitting measurements -, the correlation between measurements on models and erosion on prototypes, and validation testing done on an actual machine and its model are presented.