Supercritical water oxidation (SCWO), a promising technology to treat hazardous organic wastes, is capable of organic destruction efficiencies in excess of 99.9% at operating conditions of 620 degrees C and 234.4 bar. Under these conditions, organic compounds are completely miscible with supercritical water, oxygen, and nitrogen and oxidize rapidly to carbon dioxide and water. The reactor is central to the SCWO process. Many reactor designs have been proposed, patented, and tested at both bench and pilot scales. Commercial operation will require that these systems be scaled up by a factor of 10-100 times. Successful scale-up of this magnitude will be facilitated by creating numerical reactor models, validating these models against the available data, and then using the models to simulate the larger reactor’s performance. This paper presents the initial steps in modeling a SCWO reactor using a commercially available computational fluid dynamics (CFD) package. The results of this CFD model are compared with test data from a bench scale SCWO vessel reactor built and tested by MODAR, Inc. The calculations and test data presented in this paper are for the supercritical oxidation of ethanol. These results show good agreement with the limited experimental data available, Additional modeling with pilot-scale test data is planned.