Near the conduction threshold, the electrical conductivity of a random network exhibits power law behavior. An exponent theory modelled on the scaling theory of critical phenomena will be described, which relates the power laws which describe the various ways to approach the threshold. The particular case of finite sample size will be given special attention. The resistor lattice exponents are also relevant to more general inhomogeneous conductors. The dimensionality dependence of the conduction exponents will be reviewed.