Composites of Acrylonitrile-butadiene-styrene (ABS) and multiwall carbon nanotubes (MWNTs) have been prepared via solution-blending. The electrical conductivity of these composites is analyzed. The MWNT-filled ABS shows percolation point of the electrical conductivity at low filler loadings (1-2 wt%). The micro-structure of the composites is also analyzed by scanning electron microscopy showing that the nanotubes are dispersed quite homogeneously in the polymer-matrix. The thermogravimetric analysis is used to study the thermal degradation of ABS/MWNTs composites in nitrogen. MWNTs tend to destabilize the ABS matrix in the 220-450 degrees C degradation regions but improve the thermal stability in the 425-850 degrees C regions. With further addition of MWNTs, the features of the destabilization in the 220-450 degrees C degradation region did not change much but in the 425-850 degrees C degradation process, the MWNTs reinforced stabilization and the quality of the char residue of amorphous carbon deposition was improved. POLYM. ENG. SCI., 49:2144-2149, 2009. (C) 2009 Society of Plastics Engineers