A check analysis program initiated over twenty-five years ago is used to evaluate the performance of emission photoelectric spectrometers in five production control laboratories of the Armco Steel Corporation. For comparison, evaluation of analyses using conventional chemical methods by these same laboratories prior to instrumental analysis is also made The paper describes the check analysis program and presents analytical data used to evaluate the accuracies of the two types of photoelectric spectrometers and the conventional chemical methods used by the production laboratories.