Abstract A new nickel sulphide ore beneficiation-concentrate leach process, the HIKO process, has been developed by taking advantage of Outokump's latest flotation, leaching and solvent extraction techniques. BTR (“bottom toroidal roll”) flotation cells adaptable to on-line potential control have been used to increase the nickel/magnesium ratio of the nickel concentrate from the local Hitura mine. The hydrometallurgical treatment of the Hitura concentrate is carried out at the Outokumpu Chemical's Kokkola plant which also processes secondary nickel raw materials such as sulphate salt from the Tornio OPAR (“Outokumpu pickling acid recovery”) plant. The concentrate leaching is based on an oxygen pressure approach using autoclaves, whose design has been based on model laboratory experiments. A new solvent extraction technique has been developed to remove zinc and magnesium in a final solution purification step, to separate cobalt and nickel, and to recover nickel in the preliminary steps for cobalt and nickel salt production. It is described how a separate pre-extraction circuit is used to ensure that the main solvent extraction (SX) circuits are kept clean. Further precautions to prevent any unwanted cobalt-catalyzed oxidation of SX diluents have been taken, including a new mixer-settler design. By the use of the VSF (“vertical smooth flow”) principle, overmixing and unnecessary air contact can be avoided. During recent years the Hitura mine has benefited from an increasing number of BTR flotation cells, the introduction of which has made it possible to simplify the concentrator flowsheet. The first experience of the new leach autoclaves and the VSF mixer-settlers was gained in late 1991 when the Kokkola part of the HIKO process was started.