It is shown that accurate and reproducible measurements of oxygen in liquid steel are possible with commercial oxygen probes only if care is exercised in the make-up of the chemical and phase composition as well as the microstructure of the solid electrolytes used in these probes. To prove this premise, the second part of this study reports on evaluation of a new commercially available oxygen probe. An evaluation of the solid electrolytes used indicated that the consistency of the chemical composition, degree of stabilization, and microstructure of the electrolytes are well controlled. The application of this particular probe under industrial conditions is confirmed. Some recommendations are made as to the interpretation of the e. m. f. response curve and the use of the electronic processing unit supplied with the probe.