Foreign-body-related carcinogenesis is controversially discussed in biomaterial research. Malignancies after implantation of a huge variety of foreign bodies are well described in rodent animal models. In these models nonporous or microporous materials induce sarcoma-like tumors after an average implantation interval of 1.5 to 2 years. In this, the chemical composition of the implanted materials plays a rather minor role, the decisive factor is porosity. Basic work on this field has been performed by Oppenheimer [1-3] since the late 1940s and later by the group of Brand [4-8].