AbstractA porous ceramic, in the form of small discs, has been implanted into the upper tibiae of adult mongrel dogs in survival experiments. A similar sized disc of a metal (vitallium, titanium, or stainless steel) was also implanted, for comparison, into each tibia. The tissue specimens were studied by microangiography and correlated histology. At the 4‐month, and longer, intervals, the specimens were sectioned with the ceramic discin situ. Injected capillaries were then observed to have penetrated the ceramic.The metals became surrounded by a shell of new‐bone, lined by a fibrous membrane of varying thickness. The ceramic implants, on the other hand, appeared to have remained inert within the cancellous area of the tibiae, not surrounded by either a membrane or an osseous shell.Implications of these findings were discussed and further experiments, some of which are in progress, were propo