In conductive polymer compounds, the filler volume fraction at which a network of touching particles is formed is not a constant but depends on the manufacturing process. By applying three main features-particle-particle interaction, dynamics of agglomeration, and structure of agglomerates-which are well known in colloid science to filled polymers, the electrical percolation behavior can be understood. Thus, it is possible to explain the hitherto found low percolation thresholds of less than 0.5 vol% in carbon-black-filled resins and, hence, further reduce the threshold to 0.06 vol%.