Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). Future home and enterprise Internet users need high-bandwidth end-to-end connections that have to be provisioned automatically and dynamically. We need to make optical-layer routing as scalable and flexible as IP routing in today’s Internet to support high-end applications. We study the problem of interdomain dynamic wavelength routing based on a multidomain translucent optical network model, which allows end-to-end lightpaths to be set up not only across multiple routing domains but also through two network layers: the optical layer and the regeneration layer. In this model, a lightpath can traverse the domain boundary either through optical bypass (OOO) or through optical-electrical-optical regeneration (OEO). We propose an interdomain dynamic wavelength-routing scheme with modest computational complexity to address the problem from an algorithmic perspective. Our experimental results show that the proposed interdomain dynamic wavelength-routing scheme can (a) flexibly incorporate various cost metrics and local (or intradomain) routing schemes into a uniform interdomain routing framework, (b) effectively set up end-to-end lightpaths in a multidomain translucent network, and (c) efficiently use both optical- and regeneration-layer resources.