Future e+ e- Flavor Factories: accelerator challenges

Operation of the B-Factories (PEP-II and KEKB) has been very successful, both having exceeded their design peak and integrated luminosity and provided a huge amount of good data to the experiments. Proposal for upgrades, in order to achieve about two order of magnitude larger luminosity, are in progress in Japan, with Super-KEKB, and in Europe, with SuperB. Very high beam intensity, very short bunch length and low Interaction Point beta-functions are the key points of the Japanese design, very challenging for the hardware components (RF, vacuum). On the other hand SuperB exploits a new collision scheme, namely large Piwinski angle and "crab waist", which will allow to reach a luminosity two order of magnitude larger without increasing beam currents and decreasing bunch lengths. In this talk the present status of the two projects will be reviewed.