This National Institute of Standards and Technology (NIST) Special Publication replaces National Bureau of Standards (NBS) Letter Circular LC1132 published April 19, 1982. It reprints the Department of Commerce, NIST, Federal Register notice of December 20, 1990 titled Metric System of Measurement; Interpretation of the International System of Units for the United States (the International System of Units, abbreviated SI, is the modernized metric system); the Department of Commerce, Office of the Secretary. Federal Register notice of January 2, 1991 titled Metric Conversion Policy for Federal Agencies ; and Executive Order 12770 issued by the President of the United States on July 25, 1991 titled Metric Useage in Federal Government Programs. The first Federal Register notice restates the Department of Commerce's interpretation of the International System of Units for the United States that was last published by the Department in 1982; the second revises the Code of Federal Regulations (CFR) to remove the voluntary aspect of the conversion to the metric system of measurement for Federal agencies; and the Executive Order provides Presidential authority and direction for the use of the metric system of measurement by Federal departments and agencies in their programs. Also included is a diagram that shows graphically how the 19 SI derived units with special names are derived in a coherent manner from the SI base and supplementary units.