A cloth-sandwich construction of a carbon-carbon composite material has been implanted in the femora of a series of rats and the response of the bone to this material compared to the response to titanium. It is shown that the carbon provides for excellent hard tissue biocompatibility. When the composite has a surface texture associated with fibre run out there is a degree of bony attachment, the interfacial shear strength for the composite-bone system being significantly greater than that for the titanium-bone system during the period 4-40 weeks post implantation.