The effects of host/filler interactions, processing, and morphological development of low percolation threshold (Phi (c)) conducting blends were investigated. It was found that the value of Phi (c) was dramatically reduced by the isolation of the carbon black (CB) conducting filler at the cocontinuous interface of a binary poly(styrene) (PS) and poly(styrene co-acrylonitrile) (SAN) insulating host, resulting in a multiple percolation effect. Accumulation of the filler at the interface was possible due to the incompatibility of the CB filler with the PS phase and partial compatibility with the SAN phase. The best results were obtained by initially dispersing the CB in the PS phase during melt-blending, followed by the addition of the SAN phase.