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Histologic findings of the bone-cement junction are presented for 10 implants in rabbits and 12 human specimens. Nondecalcified sections were made, employing embedding techniques that conserve the cement. Different time periods from operation were considered. The histological approach considers mainly the distribution of the osseous elements, with a description of the sites of new and old bone, of resorptive lacunae and of fibrous tissue. Fluorescent sequential labelling of bone tissue allowed a dynamic evaluation of the viability of bone after insertion of the cement. Histologic features may be summarized as follows: In the initial phase after PMMA implantation a zone of necrosis is present around the cement. In a second phase there is very active bone formation and remodelling in the tissue adjacent to the cement, with fibrous tissue formation. Long-term adaptive bone remodelling leads to extensive resorption of cortical bone and new bone formation producing a shell around the cement with new trabeculae radiating towards the cortex.