The evaluation of the biocompatibility of biomaterials centers on appreciating the events that occur at the tissue/implant interface. In determining the biocompatibility of biomaterials, both the host response and the material response to the host must be elucidated. The in vivo biocompatibility of candidate biomaterials may be investigated using the cage implant system. The cage implant system is presented, which allows the quantitative determination of the dynamic nature of cell function at the implant site. Results from the quantitative determination of cells and products of cell activation over the implantation period can be subjected to statistical analysis methods. In addition, studies utilizing a chemotactic tripeptide have been carried out to provide an enhanced or accelerated acute inflammatory phase model. These studies are important as they provide an in vivo situation where the effect of cells on implanted materials and the effect of biomaterials on the cellular components of the inflammatory response may be investigated.