The sterilisation of biological material of an animal or human origin, which is to be used as an implant or transplant, is carried out according to a validated sterilisation method with a margin of safety of 10<6> germs. According to said method, which consists of four successive steps, harmful microorganisms are physically separated and chemically sterilised, initially in an antibiotic,then in deoxicholic acid, then in a surface-active substance and finally in primary alchol, respectively accompanied by rinsing steps involving an aqueous solution after steps two to four. As a result, a bioprosthesis sterilised with a margin of safety of 10<6> germs can be implanted without any further treatment, does not have a tendency towards calcification and offers a long service life.