Titanium dioxide (TiO2) pigments may be surface-modified by hydrous oxides, such as alumina (e.g., Cristal 134) or by organic compounds, such as organophosphate (e.g., Tiona 188). In this investigation, the effects of these pigments on the rheological properties of acrylonitrilebutadienestyrene (ABS) polymer were investigated. With the oscillatory rheometry method in the linear viscoelastic region, the storage and loss moduli versus frequency graph of ABS in the molten state showed two crossover points (COPs) when the surface of the ABS components, that is, poly(styrene-stat-acrylonitrile) and poly[(styrene-stat-acrylonitrile)-graft-polybutadiene] or g-ABS, had good interaction. The first COPs increased when the TiO2 content rose to 0.5 and 1.5% in Tiona 188 and Cristal 134 pigmented ABS samples, respectively. With the addition of TiO2 up to these contents, the polymerpigment interaction becomes stronger so that the dispersion of the pigments was good. With increasing TiO2, the first COPs dramatically decreased because of agglomeration of the pigments. The shifting of the first COP may be applied as a criterion to specify the dispersion of TiO2 particles in the ABS matrix. Scanning electron micrographs showed that the pigments had no effect on the size of the polybutadiene particles. Also, transmission electron micrographs proved that agglomerates of Tiona 188 and Cristal 134 particles were formed above 0.5 and 1.5% TiO2 contents, respectively. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012