Atomic force microscope cantilevers have been used to measure surface stress curves for gold and platinum while varying their surface free energies. To do this, the cantilevers were coated on one side with the chosen metal. They were then immersed in aqueous electrolyte solution in the standard fluid cell of an atomic force microscope. A variable potential was applied to the metal via a counter electrode. Depending on the surface potential of the metal the interfacial tension changed, causing a surface stress which bends the cantilever; the bending was detected using an optical lever with high sensitivity. The bending radius of the cantilever is a direct measure of the surface stress. For the given situation the surface stress is similar to the interfacial tension. Surface stress curves measured with gold and platinum in different electrolytes agree with results obtained with other techniques. One advantage of using atomic force microscope cantilevers is that kinetic measurements can be done. Only the resonance frequency of the cantilever limits the time resolution with which the surface stress can be measured. Typical resonance frequencies in water are 1-100 kHz.