AbstractPolycaprolactone (PCL) filled with microcrystalline cellulose (MCC), wood flour (WF), or both were characterized before and after exposure to various environmental conditions for 60 days. PCL/WF composites had the greatest tensile strength and modulus compared to neat PCL or PCL composites containing MCC. Electron microscopy indicated better adhesion between WF particles and PCL than between MCC particles and PCL. Neither wood flour nor MCC cellulose appeared to significantly affect the crystallinity of PCL. Environmental conditioning resulted in only minor deterioration of mechanical properties, although samples soaked in water had greater deterioration of mechanical properties than those in high humidity or freezing environments. After a modified 12-week soil block test, specimens made with wood flour lost weight and showed signs of decay after exposure to the brown-rot fungus Gloeophyllum trabeum.