The physical and morphological properties of articular cartilage have been used as a model for the preparation of hydrogel based synthetic analogues of this complex high water content natural hydrogel. The relatively poor strength and stiffness of simple homogeneous hydrogels have been enhanced by semi-interpenetrating polymer network (semi-IPN) technology to a level which enables the mechanical properties of natural cartilage to be approached. Maintenance of chondrocytic phenotypes at the implant interface in vitro has been found to require careful control of pore size and distribution in the hydrogel matrix. The study of synthetic techniques for the fabrication of macroporous semi-IPNs has enabled hydrogel semi-IPNs with appropriate pore sizes and mechanical properties to be produced. A range of in vitro testing techniques have been developed to enable the physico-chemical properties of these materials to be optimised prior to animal studies.