: In this paper we rst present a general lower bound on the stabilization time which holds for a number of graph theoretic problems, including leader election, spanning tree construction, the connectivity or orientation on certain interconnection networks. These bounds are of the form (D), where D is the diameter of the network. Moreover, time-optimal self-stabilizing algorithms for computing the orientation on tori, rings, hypercubes, CCC, butter ies, stars and outerplanar graphs are presented. This gives an a rmative answer to the problem 15:4 for tori stated in Tel 94b]. Key Words: stabilization time, self-stabilizing algorithm, fault-tolerance, network orientation, interconnection network, outerplanar graph, distributed system Category: C.2.4