The National Combustion Code (NCC) is being developed by an industry-government team for the design and analysis of combustion systems. CORSAIR-CCD is the current baseline reacting ow solver for NCC. This is a parallel, unstructured grid code which uses a distributed memory,message passing model for its parallel implementation. The focus of the present e ort has been to improve the performance of the NCC ow solver to meet combustor designer requirements for model accuracy and analysis turnaround time. Improving the performance of this code contributes signi cantly to the overall reduction in time and cost of the combustor design cycle. This paper describes the parallel implementation of the NCC ow solver and summarizes its current parallel performance on an SGI Origin 2000. Earlier parallel performance results on an IBM SP-2 are also included. The performance improvements which have enabled a turnaround of less than 15 hours for a 1.3 million element fully reacting combustion simulation are described.