Graph partitioning is an ubiquitous technique which has applications in many fields of computer science and engineering. Because there always exists large problem graphs which cannot fit in the memory of sequential computers and cost too much to partition, parallel graph partitioning tools have been developed. Graph ordering is the first target application of the PT-Scotch (“Parallel Threaded Scotch”) software, a parallel extension of the sequential Scotch graph partitioning and ordering tool that we are currently developing within the ScAlApplix project. We outline in this extended abstract the algorithms which we have implemented in PT-Scotch to parallelize the Nested Dissection ordering method.