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Cañon Diablo troilite (CDT), although accepted as the reference for the sulfur isotope scale, is not a Standard Reference Material manufactured for international distribution, and its sulfur isotope composition is not well characterized. We report high-precision sulfur isotope analyses of troilite from three different samples of Canon Diablo meteorite, and interlaboratory comparison of one CDT sample and of a reference SF 6 gas. The sulfur isotope composition of CDT displays a range in δ 34 S values of 0.4%., significantly larger than our analytical uncertainty (0.05%.). CDT should not be used for calibration of the sulfur isotope scale. These results support the definition of a new sulfur isotope scale relative to a hypothetical Vienna-CDT, as recently proposed by the International Atomic Energy Agency.