Poly(lactic acid) (PLA) blended with poly (butylene succinate) (PBS) was prepared in the presence of lysine triisocyanate (LTI) by using a twin-screw extruder and injection molding machine. The physical properties, rheological behavior, compatibility, and morphology were investigated by using a tensile test, a Charpy impact test, melt mass-flow rate (MFR) measurements, size exclusion chromatography (SEC), and laser scanning confocal microscopy (LSCM). The impact strength of PLA/PBS(90/10 wt %) blend composite was about 18 kJ/m(2) in the absence of LTI, and it increased to 50-70 kJ /m(2) in the presence of LTI at 0.5 wt %. The MFR value of PLA/PBS(90/10 wt %) decreased from 25 g/10 min at 200 degrees C in the absence of LTI to approximately 3 g/10 min in the presence of LTL These results imply that isocyanate groups of LTI reacted with both terminal hydroxyl or carboxyl groups of the polymers. Spherical particles at 1 mu m were observed by using LSCM in the presence of LTI. These results indicate that the LTI is a useful reactive processing agent to increase the compatibility of PLA/PBS blend composites to increase the impact strength of PLA. (C) 2007 Wiley Periodicals, Inc.