Ion-implantation can increase the electrical conductivity of the polymer poly (p-phenylene sulfide) (PPS) by ~ 14 orders of magnitude. This conductivity increase, which is stable under ambient conditions, is studied as a function of temperature, ion energy, fluence and species, using a novel technique, based on microelectronics processing, capable of accurately measuring conductivities as low as 10−10 (Ω-cm)−1. Mechanisms for the enhanced conductivity of PPS are discussed in relation to our measurements.