Abstract: Superconductivity in mesoscopic systems is supressed by quantum fluctuations. Dissipation actually restores superconductivity in such systems. This interplay, however, is not yet well understood. Examples of that are the breakdown of superconductivity in low dimensional superconductors, and in particular, the normal-to-superconducting transition observed in nanowires. In this talk we present a new theory of the superconductor-metal transition of resistively shunted junctions. this theory takes mesoscopic effects into account using a phenomenological two-fluid model of superconducting grains. Using this model, we describe transport through a single grain, and a chain of grains connected by resistively shunted Josephson junctions. Finally, we will consider the possible concequences of our theory for superconducting nanowires.