A scanning reference electrode technique has been developed to study intergranular corrosion of austenitic stainless steels. The potential variations produced in the electrolyte due to the intergranular corrosion of the sensitized grain boundaries have been measured by scanning a microtip reference electrode across the heat-affected zone adjacent to a weld. The development of a test based on the scanning reference electrode technique for determining the degree of sensitization of stainless steels has been explored. The technique is particularly useful in determining the degree of sensitization and the location of the sensitized grain boundaries adjacent to welds. The effect of material and welding variables on the location and degree of sensitization has been studied. The results have been compared with conventional tests for detecting susceptibility to intergranular corrosion.