This work describes and studies a process for electrolytic deposition of a mercury monolayer on a carbon fiber electrode. Exceptional sensitivity for the determination of Pb2+ is demonstrated when the mercury-monolayer-on-carbon electrode (MMCFE) is used with fast (nu>1 kV/s) anodic stripping voltammetry. Investigation of the nature of the analytical signal revealed that the high sensitivity is due to ionization of Pb atoms in the mercury layer, which catalyzes the oxidation of atomic hydrogen adsorbed at the Hg layer. For a 1 s preconcentration time at a cylinder electrode (A = 1.1 x 10(-3) cm(2)), the calculated detection limit (3 std. dev. of baseline noise) is 80 fM, corresponding to ca. 1 zeptomole of Pb. (C) 2009 Elsevier B.V. All rights reserved.