The aim is to show how seismic risk analysis of lifeline networks can be performed efficiently without loss of accuracy. Two efficient schemes have been developed to find the probabilities of partial network failure due to threats coming from a given set of seismically active source areas and/or faults with known seismic history. Networks with deterministic link resistances and those with random link resistances can be analyzed. Both schemes start with the transformation of the given network and its objective to an equivalent SSP network which is simpler to handle and has a certain number of tie-sets. Then the probability that any desired number of these tie-sets fail simultaneously in any given year is evaluated. An efficient computer program for the deterministic resistance approach has been developed and tested on several pilot problems. The network of major highways surrounding the Boston, Massachusetts area is analyzed, and the results are presented herein.