The present invention refers to a chemical mixture for the stabilization and conservation of organic material, preferably of human nature, such as for example cells and nucleic acids. In particular, the invention is relative to a mixture that makes it possible to stabilize and conserve at ambient temperature for a few days cells and/or nucleic acids isolated from a sample of human biological fluids such as, for example, whole blood. The mixture is characterized by the presence of siloxanic polymers.