Abstract Following the development of two phase helico axial pumps in the seventies a R&D program has recently been launched by IFP and DBGP for the development of two phase helico axial turbines. These turbines may be used in many process applications in replacement of let down valves for energy recovery but also to increase the cooling duty or the liquid production. They may also be used in systems including a two phase separator with single phase turbines or valves at its outlets in view of reducing the number of equipment, space and weight. These turbines, suitable for all gas fractions, may find applications in the hydrocarbon upstream field (HP/HT wells, fractured reservoirs, oil stabilisation, electricity production in remote areas) or in the hydrocarbon downstream field (refrigeration cycles, LNG, gas drying, solvent regeneration or hydrotreatment units). This wide potential field of applications requires helico axial turbines to be suitable for a broad range in flow rate, pressure, temperature and gas fraction. This has several consequences on the pump design, particularly, regarding the mass transfer occurring during the pressure let down and the volume change across a turbine or a hydraulic stage. A two phase helico axial turbine prototype will be tested, in single and two phase flows, during the second half of 2003 to confirm the expected hydraulic performance.