The main contribution of this work is to propose a distributed on-demand routing and wavelength assignment algorithm for WDM networks. The proposed algorithm, termed WDM-DSR, is capable to select routes and establish light-paths via message exchanges without imposing a major overhead on the network. Also, we show that the proposed scheme can be used to balance the load in a WDM network. The simulation results show that the proposed solution is comparable with the other algorithms that demands for a much higher computational and message costs. © 2009 IEEE.