The B-Mode of the Cosmic Microwave Background Polarization (CMBP) promises to detect the gravitational wave background left by Inflation and explore this very early period of the Universe. In spite of its importance, however, the cosmic signal is tiny and can be severely limited by astrophysical foregrounds. In this contribution we discuss about one of the main contaminant, the diffuse synchrotron emission of the Galaxy. We briefly report about recent deep observations at high Galactic latitudes, the most interesting for CMB purposes because of the low emission, and discuss the contraints in CMBP investigations. The contamination competes with CMB models with T/S = 10^{-2}--10^{-3}, close to the intrinsic limit for a 15% portion of the sky (which is T/S ~ 10^{-3}). If confirmed by future surveys with larger sky coverage, this gives interesting perpectives for experiments, that, targeting selected low emission regions, could reach this theoretical limit.
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