This paper presents recent attainments of one of the main components of the POSEIDON project launched in 1984 by TOTAL, IFP and STATOIL : the multiphase pump. After successful bench tests, the pump had been installed on a real field in Tunisia. Four thousand running hours without mechanical problems have provided a better understanding of how a multiphase pump behaves when placed in a production network. INTRODUCTION With the necessary development of small oil accumulation, either onshore or offshore and the increasing depth of offshore exploration especially in Brazil and in the Gulf of Mexico, it is widely accepted that there will be a need to pump the effluent from the wellhead to the nearest processing facility without treatment on site. This results from both a technical limitation of the traditional platforms when faced with deeper waters and from economic considerations of lower cost offered by this new technique. For shallower waters, even when a platform could be envisaged, the size of the accumulations often rules out the development because of economic constraints. As the maximum possible distance that can be covered by a multiphase effluent with the natural pressure appears to be limited to about 15/20 km of pipe line (15 km for DON, BP), a satellite developments could use a new type of technology to add energy to the flow at the beginning of the line. The available economic studies [I] show that the majority of reserves in the North Sea are at a distance of 50 km or less from existing facilities, and that 80% of the discoveries with a total of 10 million of barrels of reserves are located withing 35 km of them, thus giving access to additional oil at acceptable cost, should an industrial boosting technique be made available to the operators. The POSEIDON project was created in 1984 by TOTAL, IFP and STATOIL to review all the problems to be solved to build a multiphase subsea station. One of the major element of such a station was the multiphase pump. At that time no pump capable of handling a multiphase fluid was available and hence a major effort was agreed upon by the associates to develop an emerging technology in order to reach a very ambitious goal : a pump able to create a differential pressure on any liquid, with a gas fraction from O to 95% in steady state flow and the capability of handling void fraction of 100% in case of slugs of pure gas. The available technology of the end at the 70?s was an ESP (electric submersible pump) able to pump a fluid with GLR of 3(gas to liquid ratio) under down hole conditions. Today the POSEIDON multiphase pump is industrially proven, has