A liquid-liquid centrifugal separator has been modified for possible application as a downhole method for separating crude oil from produced water. Centrifugal separators of various sizes (from 2- to 25-cm rotor diameter) have been built and operated over the past decades at various U.S. Department of Energy facilities. These units have several characteristics that make them attractive for downhole applications, including excellent phase separation, reliability in remote applications with >20,000 h of operation prior to maintenance, and the ability to handle high volumetric throughput with a very low residence time. These separators consist of a rotating cylinder in which the two phases are separated and a stationary housing that collects the separated streams. This paper discusses some of the aspects of the alterations required for downhole operation. Specifically, we discuss modifications of the exterior housing allowing for greater flow through the system. The system presented here improves the performance of a standard separator by 140%.