We have developed a biodegradable particulate composite bone cement consisting of a poly(propylene glycol-fumarate)-(methylmethacrylate) matrix mixed with calcium carbonate and tricalcium phosphate particulates. Previous ex-vivo studies suggest that this system provides sufficient strength for a number of potential clinical applications including structural reinforcement of osseous defects, supplementation of internal fixation of age-related fractures, and delivery of antibiotics to treat osteomyelitis. Ex-vivo degradation assays have also shown that the cement approximates physiologic conditions of bone remodeling as it degrades. In order to evaluate the in-vivo responses to this material, we implanted cement specimens subcutaneously in rats for up to 84 days. Compressive strength of the subcutaneous implants increased linearly through day 21 to 4.91 MPa, then decreased linearly by day 84 to less than 1 MPa. We conclude that this PPFMMA system is biocompatible and biodegradable, and has the potential for use as an orthopedic bone cement. Future studies will be directed toward characterizing the intraosseous histological response and at coordinating the rate of cement degradation with bony ingrowth.