The differentiation of mesenchymal tissue into bone tissue when in contact with different forms of calcium phosphate ceramics implanted within intraskeletal sites in different animals has been reported. The osteogenic effects of calcium phosphate ceramics have been demonstrated in several animal species. Four biopsies from HA-ceramics were obtained, implanted in bony sites of humans, which failed to be osteointegrated for more than one year. Two kinds of ceramics with different characteristics were studied. A histological analysis of the soft tissue/ceramic interface was carried out. The ceramics were embedded in an identical connective tissue. The interface with the ceramic consisted of collagen bundles parallel to the ceramic surface. Certain ceramics showed at their surface, a tissue matrix with the staining abilityof bone, although no evidence of osteogenic cells or osteoid was foundat the matrix surface.The pores were filled with a hyaline tissue containing a few cells dispersed within the hyaline matrix. Although this study could not be performed under the same conditions as in animals, no bone formation was induced by these ceramics implanted in the connective tissue suggesting that, in humans the osteogenic effect of this material is inconstant, or related to specific characteristics.