The understanding of the in vivo performance of synthetic materials is largely dependent upon a profound knowledge of the properties of the materials in question. Analogous to materials science in its broadest sense, the basis for biomaterials science is formed by microstructural there. It is therefore, that in this series on structure property relationships in biomaterials a substantial part is devoted to the analysis of the basic properties of the various synthetic biomaterials. In addition, the effect of microstructural aspects on properties is considered at great length.