One major objective of the European project "Collaborative Harmonisation of Methods for Profiling of Amphetamine Type Stimulants" (CHAMP) funded by the sixth framework programme of the European Commission consisted in the harmonisation of a Gas Chromatography / Mass Spectrometry (GC/MS) method for the analysis of organic impurities found in 3,4-MethyleneDioxyMethAmphetamine (MDMA) samples in a drug intelligence perspective. Statistical analysis provided a selection of pertinent variables among the 46 organic impurities identified in the chromatograms. Correlation coefficients were used to yield separation between populations of linked samples (from the same seizure) and unlinked samples (from different seizures). It was shown that correlation measurements based on Pearson and cosine functions applied to the data pre-treated by the square root provided an excellent discrimination between the two populations. The organic impurities profiling method was proved to be an excellent technique to differentiate samples from different seizures and to highlight operational links between samples.