In order to achieve better understanding and better predictive models for three-phase systems, Norsk Hydro ASA has designed and built a unique industrial-scale test facility for investigations of such systems. The test facility includes a 200 m long 3″ diameter flow loop where a section can be tilted upwards or downwards. The fluids can be any combination of real hydrocarbon oil, gas and water (with salts included) as long as the partial pressures of CO 2 and H 2S are below 20 bar and 0.05 bar, respectively. The maximum operating temperature and pressure are 140 ∘C and 110 bar absolute, respectively. The test facility is designed to implement total control of both flow conditions and system chemistry. This makes it possible to undertake investigations on the phenomena that occur in multiphase flow. It is optional to add production chemicals to the process fluid. The test facility is presented in detail with descriptions of the chosen solutions, the instrumentation and the range of possible applications. It has successfully undertaken tests with a large range of well fluids from the North Sea, and a listing of these tests is included.