Adhesion force measurements are used to determine potential dependence of the force of adhesion between a Si3N4 cantilever and an Au surface in basic solution. At both positive and negative potentials, the force curve is dominated by van der Waals contributions, indicating that there is little specific interaction between the tip and the sample. However, at intermediate potentials (between 0.4 and 0.6 V vs SHE) the tip-sample interaction is dominated by an adhesive component, the magnitude of which is approximately 2 kJ/mol; this corresponds to the expected strength of a hydrogen bond between O- groups on the tip and AuOH on the surface.