A method for the surface area determination of metallic ruthenium was tested, It was based on oxidation of the prereduced catalyst in a liquid suspension with chromate and with potentiometric indication, It was shown that, as compared with a standard BET measurement of metal blacks, such a technique gave excellent results, especially for ruthenium black and SiO2- and Al2O3-supported catalysts, These supports did not follow redox surface changes, On the other hand the method was less accurate for active carbon-supported ruthenium, since a considerable volume of the titrating agent was consumed by support surface composition changes.