Poly(lactic acid) (PLA)/SiO2 nanocomposites were prepared via melt mixing with a Haake mixing method. To improve the dispersion of nanoparticles and endow compatibility between the polymer matrix and nanosilica, SiO2 was surface-modified with oleic acid (OA). The interfacial adhesion of the PLA nanocomposites was characterized by field-emission scanning electron microscopy. The storage modulus and glass-transition temperature values of the prepared nanocomposites were measured by dynamic mechanical thermal analysis. The linear and nonlinear dynamic rheological properties of the PLA nanocomposites were measured with a parallel-plate rheometer. The effects of the filling content on the dispersability of the OA-SiO2 nanoparticles in the PLA matrix, the interface adhesion, the thermomechanical properties, the rheological properties, and the mechanical properties were investigated. Moreover, the proper representation of the oscillatory viscometry results provided an alternative sensitive method to detect whether aggregation formed in the polymeric nanocomposites. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2866-2873, 2010