One of the challenging issues in optical networks is call blocking and it increases with the number of lightpath requests due to the limited number of wavelength channels in each fiber link. This chapter introduces a priority based routing and wavelength assignment (PRWA) scheme in order to reduce call blocking in the network. The introduced PRWA scheme serves the lightpath requests for routing and wavelength assignment according to their priority order. The priority order of each lightpath request is estimated based on type of path (direct link physical path or indirect link physical path) first and then the traffic volume. If the priority order of lightpath requests is estimated using these criteria, blocking of lightpath requests due to wavelength continuity constraints can be reduced to a great extent, which leads to better performance of the network in terms of lower call blocking. The simulation results indicate that the introduced PRWA scheme outperforms the conventional non-priority based routing and wavelength assignment scheme (NPRWA) in terns of blocking probability.