The process of inducing differentiated and undifferentiated cells to become osteogenic using demineralized bone powder (DBP) is a well-known phenomenon in developmental biology. The aim of this study was to examine whether age has an effect on the process of bone induction. DBP was implanted in the subcutaneous thoracic tissue of young rats (28-56 days) and old rats (14 months or older), and the animals were examined seven, 12, 20, and 60 days after implantation. The amount of newly induced bone in the implant was quantitatively measured using histomorphometry and 45Ca uptake. Undecalcified and decalcified specimens were processed for histologic examination using several stains that demonstrate osteoid. Both the young rats and the old rats formed bone in response to the DBP implants. In old animals the induced bone appeared to be less in quantity, it formed at a slower rate, and it exhibited less bone marrow cellularity than did the bone in young animals.