The Proficiency Test for Chemical Analysis of Iron Ore was established in 1992 at the 17th meeting of the ISO/TC 102/SC2 (ISO, 2008) committee. This program which is coordinated by CSIRO has now been active for 33 years, providing participants with valuable assessment of the analytical performance of their laboratory. This proficiency test is unique in that most samples distributed are not certified reference materials but are real production materials, prepared in a production laboratory and donated to the program by iron ore producers. Variation in the physical properties of real-world samples, such as particle size distribution, can influence digestion efficiency and homogeneity. Compared to certified reference materials, these samples present an analytical challenge to participating laboratories and are a true test of the robustness of their analytical methods with regards to sample preparation. Throughout the course of the program, the geographical distribution of participants has closely matched the geographical distribution of industry stakeholders (both iron ore producers and customers). Also, the country of origin for the samples provided for each round has closely matched the export market share distribution worldwide. With data provided from all major stakeholders and all major sample sources accounted for, this means that this data set can be considered strongly indicative of industry analytical performance and iron ore quality over time. As part of the program, most participants specify the analytical methods that they use. Comparison of the performance of each of these methods separately can further be made to determine the most precise method for each analyte and the difference between methods.