A continuous oxygen probe,incorporating a SIRO2 solid electrolyte oxygen sensor which measured the oxygen potential of a small volume of gas enclosed above the melt's surface,was constructed and tested. The oxygen potential of iron-silicate slags in equilibrium with solid iron in the temperature range 1250 to 1300C were measured continuously for tests of up to 40 hours duration. Results were in agreement with those of previous workers using gas equilibration techniques. Tests on non- iron buffered slags proved unsuccessful due to corrosion of the probe's component in contact with the slag and an alternative material is Required.