The invention relates to a new process for decontaminating a biological material by partitioning and inactivation techniques. The process comprises the formation of a three-layer liquid system (a-b-c), where the layers are placed one onto the other and are different from each other in density and/or miscibility properties； the upper layer (a) comprises an aqueous solution of the biological material to decontaminate； the lower layer (c) comprises the solution inactivating said viruses, prions or bacteria； the intermediate layer (b), interposed between said upper and lower layers, separates and protects the biological material from the inactivating solution； it is studied so as to maximize the stability of the three-layer system in all the steps of the decontamination process； it comprises an organic solvent (or a mixture of more such solvents), immiscible at least with the upper layer； preferred organic solvents and their mixing proportions are specified in the description. Moreover, the invention provides specific indications about the density difference between the layers in order to preserve system stability and, at the same time, protect the efficiency of decontamination and the biological activity of the material undergoing decontamination.
