The local injection and lateral propagation of charge in ultrathin polyaniline (PAN) layers have been studied with the scanning electrochemical microscope (SECM). Monolayers of PAN were deposited on a glass substrate using the LB method and were chemically reduced using sodium dithionite. A microelectrode held close to the PAN layer was used to generate a flux of an oxidant, i.e., Fe(phen)(3)(3+) (phen = 1,10-phenanthroline) which diffused to the surface and locally oxidized the reduced PAN. By simulating the current-time transients, the kinetics of lateral charge propagation have been evaluated.