This work presents an insight into the conductivity-carbon black (CB) concentration relationship of nanocomposites. High conductivity is observed above 14% CB loading (% on mass of epoxy resin), indicating the generation of conductive networks throughout the nanocomposites. Observation of the relationship between the natural logarithm of conductivity values versus CB loading shows a remarkable increase in conductivity when the CB loading increases from 19 to 24%. In this region (percolation) a relatively small increase in CB loading produces a large increase in conductivity. When the quantity of CB is low (< 14%), the resistivity of the nanocomposite is only slightly different from that of the base polymer; further increase in CB loading beyond the critical concentration region (> 24%) causes marginal change in conductivity. The uniformity of the nanocomposites is evidenced by both microstructure (Si-mapping) and macro-property (resistance versus distance relationship) analyses.