Among different methods for preparation of rubberclay nanocomposites, melt intercalation and latex-coagulation methods are more practiced. In this study, dispersion of pristine nanoclay by the latex-coagulation method and organically modified nanoclay by the melt-intercalation method in styrene butadiene rubber were compared, based on the same amount of mineral clay in the composites. Dispersion of nanoclay was examined by X-ray diffraction before and after vulcanization, and by atomic force microscopy after vulcanization. It was shown that final structure of nanoclay in the composites was intercalated by both methods, with better dispersion resulting from coagulation of latex over mixing in the melt state. Dynamicmechanicalthermal analysis and tension tests were used to further assess dispersion and polymerfiller interactions. These tests confirmed better dispersion and larger interfacial area for pristine nanoclay in the latex-coagulated rubber through observing lower peak loss factor, higher growth of stress in stretching, and lower elongation at break when compared with those for the nanocomposite prepared by the melt mixing. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012