In this course, theoretical and practical approaches to quantifying and presenting the highly precise stable isotope measurements arising from modern gas, thermal-ionization, and ICP source multicollector mass spectrometers and optical spectrometers and their associated off-line and on-line sample processing procedures will be discussed. The evolution of isotope metrology, from the calibration of isotopic analytical systems to the role of and often unique qualities of standards and reference materials will be explored. The proper use and implementation of international isotopic scales, from their definitions to the traceability bridges they provide, coupled with approaches to uncertainty estimation will also be examined.