Nanocomposite materials were obtained using a latex of natural rubber as the matrix and an aqueous suspension of waxy maize starch nanocrystals as the reinforcing phase. Starch nanocrystals were obtained after sulfuric acid hydrolysis of waxy maize starch granules. They consisted of crystalline platelets 6-8 nm thick, 40-60 nm long, and 15-30 mn wide. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was cast and evaporated. The solid nanocomposite films were characterized using scanning electron microscopy, water and toluene absorption experiments, differential scanning calorimetry, and wide-angle X-ray diffraction analysis. The barrier properties of the nanocomposites to water vapor and oxygen were also investigated, and the effect of surface chemical modification of starch nanocrystals was studied.