The in vitro degradation behavior of a series of resorbable, bioactive nano- and microcomposites designed for orthopaedic application is explored. Nanoparticles of alpha-tricalcium phosphate are significantly more effective than the equivalent microparticles in reducing heterogeneity of the Poly(D,L-lactide-co-glycolide) degradation. More uniform degradation, reduced acid release, and less swelling of polymer were observed.