We present a theoretical and numerical study of the connectivity of fault networks following power law fault length distributions, n(l)~&agr;l-a, as expected for natural fault networks. Different regimes of connectivity are identified depending on a. For a>3, faults smaller than the system size rule the network connectivity and classical laws of percolation theory apply. On the opposite, for a<1, the connectivity is ruled by the largest fault in the system. For 1 both small and large faults control the connectivity in a ratio which depends on a. The geometrical properties of the fault network and of its connected parts (density, scaling properties) are established at the percolation threshold. Finally, implications are discussed in the case of fault networks with constant density. In particular, we predict the existence of a critical scale at which fault networks are always connected, whatever a smaller than 3, and whatever their fault density.¿ 1997 American Geophysical Union