[en] Current practices were examined for calibrating and/or determining biases for the principal nuclear material measurement systems in use by the nuclear industry: uranium gravimetry, uranium determination by reduction-oxidation titrimetry, plutonium determination by amperometric titration, isotopic analysis by mass spectrometry, isotopic-dilution assay of iron and plutonium, uranium fluorometry, iron spectrophotometry, mass measurements, volume measurements, flow measurements, nondestructive assays, and holdup measurements. A number of frequently used methods are described in this report. The principles, procedures, apparatus, applications, and calibration for each are discussed. The sources of measurement bias are identified, also the expected magnitudes of errors associated with the methods