The U. S. Naval Observatory operates optical instruments to determine Earth rotation parameters, and, in conjunction with the U. S. Naval Research Laboratory, began to use the connected-element interferometer at Green Bank, West Virginia in October, 1978 for the determination of these data. Preliminary analysis shows that the results from both techniques may be used together to provide improved Earth rotation parameters. The observations of both methods suffer from possible annual periodic differences. It is most important that observations be continued with all techniques in an effort to establish the exact nature of systematic differences and to evaluate the consistency of these errors over long periods of time.