Directive 2003/17/EC of the European Parliament and the European Council stipulates that petrol (gasoline) with a total sulfur content below 10 mg kg(-1) must be available in all European Union member states by 2009. Three certified reference materials were produced in support of this directive in a joint effort of the members of the European Reference Materials Initiative (ERM). Two of the materials were made from commercial petrol, while the third one was prepared from a blend of commercial petrols. Relative between-ampule heterogeneity of the materials was quantified and found to be below 2.5%. Potential degradation during storage and dispatch was quantified, and shelf lives based on these values were set. The three materials were characterized by three institutes using different variants of isotope-dilution mass spectrometry. The results from the three institutes were combined, and the final uncertainties of the respective sulfur mass fractions were estimated including contributions from heterogeneity, stability, and characterization. The following mass fractions were derived: ERM-EF211, 48.8 +/- 1.7 mg kg(-1); ERM-EF212, 20.2 +/- 1.1 mg kg(-1); and ERM-EF213, 9.1 +/- 0.8 mg kg(-1).