This invention relates to a hydrometallurgical process for extracting platinum group metals (PGMs), gold, silver and base metals from a flotation concentrate (10) containing sulphide minerals such as pentlandite and chalcopyrite, along with pyrite and pyrrohotite. The process includes a modified pressure oxidation step (12) to selectively separate base metals into sulphate medium (14), from the PGMs. The modified pressure oxidation step (12) partially or completely oxidizes sulphide minerals to produce a product slurry (14) containing base metal sulphates in solution and a solid residue containing PGMs along with sulphate and elemental sulphur. The solid residue is subjected to a thermal treatment (18) to remove sulphate and elemental sulphur from the solid residue, and to condition the PGMs to be soluble in chloride medium. The treated solid residue is the subjected to PGM recovery by leaching in chloride leaching medium (20) to recover the PGMs.