The aim of this talk is to illustrate the results of recent
theoretical studies on the role of the Galactic magnetic field in the
star formation process, focusing in particular on the effects of
magnetic braking on the evolution of circumstellar disks and the
related issue of magnetic field dissipation.

The talk will point out the limitations of the classic ideal-MHD
description of the star formation process and the need to include the
effects of magnetic dissipation (collisional and/or turbulent
resistivity) in current models for the collapse of molecular clouds
and the formation/evolution of accretion disks around young stars.