Impurities found in various sources of precursors (sassafras oil, safrol, isosafrol, piperonal), intermediates (beta-nitroisosafrol, piperonylmethylketone (PMK)) and final product (3,4-methylenedioxymethamphetamine (MDMA)) are presented and discussed. Particular attention is paid to the chemical origin of each impurity found in the prepared samples. Impurity profiles of isosafrol, piperonal, and PMK samples obtained from industrial sources or from sassafras oil were first compared. Then PMK samples produced from isosafrol through isosafrol glycol or through beta-nitroisosafrol were compared. At last, attention was paid to the reductive amination of PMK to MDMA using different reductive agents. Possible use of this profiling method to determine the synthesis route is discussed for all products.