The flammability and synergistic flame-retardant effects of fumed silica (SiO(2)) in ethylene vinyl acetate (EVA)/aluminum hydroxide (ATH) blends were studied with limiting oxygen index measurements, UL 94 testing, cone calorimeter testing (CONE), and thermogravimetric analysis (TGA). The results show that the addition of a given amount of fumed SiO(2) can apparently improve UL 94 rating. The CONE data indicated that the addition of fumed SiO(2) greatly reduced the heat release rate. The TGA data showed that this synergistic flame-retardant mechanism of fumed SiO(2) in the EVA/ATH materials was mainly due to the physical process. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1285-1289, 2011