In modeling communication networks by graphs, the problem of designing s-fault-tolerant networks becomes the search for s-Hamiltonian graphs. This thesis is a study of the s-Hamiltonian index of a graph G.;A path P of G is called an arc in G if all the internal vertices of P are divalent vertices of G. We define l (G) = max{lcub}m : G has an arc of length m that is not both of length 2 and in a K3{rcub}. We show that if a connected graph G is not a path, a cycle or K1,3, then for a given s, we give the best known bound of the s-Hamiltonian index of the graph
