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.Linvention porte sur un nouveau procédé de décontamination dun matériau biologique par des techniques de séparation et dinactivation. Le procédé comprend la formation dun système liquide à trois couches (a-b-c), où les couches sont placées lune sur lautre et sont différentes lune de lautre en termes de densité et/ou de propriétés de miscibilité. La couche supérieure (a) comprend une solution aqueuse du matériau biologique à décontaminer. La couche inférieure (c) comprend la solution dinactivation des virus, prions ou bactéries. La couche intermédiaire (b), interposée entre les couches supérieure et inférieure, sépare et protège la matière biologique de la solution dinactivation. Il est étudié de façon à maximiser la stabilité du sys
