We have fabricated atomic-scale metal wires with quantized conductance in electrolytes and studied double layer charging, anionic adsorption and surface stress effects on the quantum transport in the wires. In the double layer charging regime, the conductance changes linearly with the potential, which can be attributed to a change in the amount of electron spill-out of the wire. A large change in the potential results in a substantial stress in the wires, causing atoms in the wires to rearrange. Upon anionic adsorption, the conductance decreases due to the scattering of conduction electrons by the adsorbed anions. (C) 2003 Elsevier Ltd. All rights reserved.